feat():initial version

install/boost_1_75_0/include/boost/contract/detail/assert.hpp

@@ -0,0 +1,28 @@
+
+#ifndef BOOST_CONTRACT_DETAIL_ASSERT_HPP_
+#define BOOST_CONTRACT_DETAIL_ASSERT_HPP_
+
+// Copyright (C) 2008-2018 Lorenzo Caminiti
+// Distributed under the Boost Software License, Version 1.0 (see accompanying
+// file LICENSE_1_0.txt or a copy at http://www.boost.org/LICENSE_1_0.txt).
+// See: http://www.boost.org/doc/libs/release/libs/contract/doc/html/index.html
+
+#include <boost/contract/core/exception.hpp>
+#include <boost/contract/detail/noop.hpp>
+#include <boost/preprocessor/stringize.hpp>
+
+// In detail because used by both ASSERT and CHECK.
+// Use ternary operator `?:` and no trailing `;` here to allow `if(...) ASSERT(
+// ...); else ...` (won't compile if expands using an if statement instead even
+// if wrapped by {}, and else won't compile if expands trailing `;`).
+#define BOOST_CONTRACT_DETAIL_ASSERT(cond) \
+    /* no if-statement here */ \
+    ((cond) ? \
+        BOOST_CONTRACT_DETAIL_NOOP \
+    : \
+        throw boost::contract::assertion_failure( \
+                __FILE__, __LINE__, BOOST_PP_STRINGIZE(cond)) \
+    ) /* no ; here */
+
+#endif // #include guard
+

install/boost_1_75_0/include/boost/contract/detail/auto_ptr.hpp

@@ -0,0 +1,53 @@
+
+#ifndef BOOST_CONTRACT_DETAIL_AUTO_PTR_HPP_
+#define BOOST_CONTRACT_DETAIL_AUTO_PTR_HPP_
+
+// Copyright (C) 2008-2018 Lorenzo Caminiti
+// Distributed under the Boost Software License, Version 1.0 (see accompanying
+// file LICENSE_1_0.txt or a copy at http://www.boost.org/LICENSE_1_0.txt).
+// See: http://www.boost.org/doc/libs/release/libs/contract/doc/html/index.html
+
+#include <boost/contract/detail/operator_safe_bool.hpp>
+#include <boost/contract/detail/debug.hpp>
+#include <boost/config.hpp>
+
+namespace boost { namespace contract { namespace detail {
+
+// Using this instead of std::auto_ptr because std::auto_ptr will be removed in
+// C++17 (this library always uses release() to avoid ownership issues).
+template<typename T>
+class auto_ptr { // Copyable (using default copy operations).
+public:
+    explicit auto_ptr(T* ptr = 0) : ptr_(ptr) {}
+
+    ~auto_ptr() BOOST_NOEXCEPT_IF(false) { delete ptr_; }
+
+    T* release() {
+        T* ptr = ptr_;
+        ptr_ = 0;
+        return ptr;
+    }
+
+    T& operator*() {
+        BOOST_CONTRACT_DETAIL_DEBUG(ptr_);
+        return *ptr_;
+    }
+    
+    T const& operator*() const {
+        BOOST_CONTRACT_DETAIL_DEBUG(ptr_);
+        return *ptr_;
+    }
+
+    T* operator->() { return ptr_; }
+    T const* operator->() const { return ptr_; }
+
+    BOOST_CONTRACT_DETAIL_OPERATOR_SAFE_BOOL(auto_ptr<T>, !!ptr_)
+
+private:
+    T* ptr_;
+};
+
+} } } // namespace
+
+#endif // #include guard
+

install/boost_1_75_0/include/boost/contract/detail/check.hpp

@@ -0,0 +1,48 @@
+
+#ifndef BOOST_CONTRACT_DETAIL_CHECK_HPP_
+#define BOOST_CONTRACT_DETAIL_CHECK_HPP_
+
+// Copyright (C) 2008-2018 Lorenzo Caminiti
+// Distributed under the Boost Software License, Version 1.0 (see accompanying
+// file LICENSE_1_0.txt or a copy at http://www.boost.org/LICENSE_1_0.txt).
+// See: http://www.boost.org/doc/libs/release/libs/contract/doc/html/index.html
+
+#include <boost/contract/core/config.hpp> 
+#ifndef BOOST_CONTRACT_NO_CHECKS
+    #include <boost/contract/core/exception.hpp>
+
+    /* PRIVATE */
+
+    #ifndef BOOST_CONTRACT_ALL_DISABLE_NO_ASSERTION
+        #include <boost/contract/detail/checking.hpp>
+        #include <boost/contract/detail/name.hpp>
+
+        #define BOOST_CONTRACT_CHECK_IF_NOT_CHECKING_ALREADY_ \
+            if(!boost::contract::detail::checking::already())
+        #define BOOST_CONTRACT_CHECK_CHECKING_VAR_(guard) \
+            /* this name somewhat unique to min var shadow warnings */ \
+            boost::contract::detail::checking BOOST_CONTRACT_DETAIL_NAME2( \
+                    guard, __LINE__);
+    #else
+        #define BOOST_CONTRACT_CHECK_IF_NOT_CHECKING_ALREADY_ /* nothing */
+        #define BOOST_CONTRACT_CHECK_CHECKING_VAR_(guard) /* nothing */
+    #endif
+    
+    /* PUBLIC */
+    
+    #define BOOST_CONTRACT_DETAIL_CHECK(assertion) \
+        { \
+            try { \
+                BOOST_CONTRACT_CHECK_IF_NOT_CHECKING_ALREADY_ \
+                { \
+                    BOOST_CONTRACT_CHECK_CHECKING_VAR_(k) \
+                    { assertion; } \
+                } \
+            } catch(...) { boost::contract::check_failure(); } \
+        }
+#else
+    #define BOOST_CONTRACT_DETAIL_CHECK(assertion) {}
+#endif
+
+#endif // #include guard
+

install/boost_1_75_0/include/boost/contract/detail/checking.hpp

@@ -0,0 +1,82 @@
+
+#ifndef BOOST_CONTRACT_DETAIL_CHECKING_HPP_
+#define BOOST_CONTRACT_DETAIL_CHECKING_HPP_
+
+// Copyright (C) 2008-2018 Lorenzo Caminiti
+// Distributed under the Boost Software License, Version 1.0 (see accompanying
+// file LICENSE_1_0.txt or a copy at http://www.boost.org/LICENSE_1_0.txt).
+// See: http://www.boost.org/doc/libs/release/libs/contract/doc/html/index.html
+
+#include <boost/contract/core/config.hpp>
+#include <boost/contract/detail/static_local_var.hpp>
+#include <boost/contract/detail/declspec.hpp>
+#include <boost/thread/mutex.hpp>
+#include <boost/noncopyable.hpp>
+#include <boost/config.hpp>
+
+namespace boost { namespace contract { namespace detail {
+
+#ifdef BOOST_MSVC
+    #pragma warning(push)
+    #pragma warning(disable: 4275) // Base w/o DLL spec (noncopyable).
+    #pragma warning(disable: 4251) // Member w/o DLL spec (mutex_ type).
+#endif
+
+// RAII facility to disable assertions while checking other assertions.
+class BOOST_CONTRACT_DETAIL_DECLSPEC checking :
+    private boost::noncopyable // Non-copyable resource (might use mutex, etc.).
+{
+public:
+    explicit checking() {
+        #ifndef BOOST_CONTRACT_DISABLE_THREADS
+            init_locked();
+        #else
+            init_unlocked();
+        #endif
+    }
+
+    ~checking() {
+        #ifndef BOOST_CONTRACT_DISABLE_THREADS
+            done_locked();
+        #else
+            done_unlocked();
+        #endif
+    }
+    
+    static bool already() {
+        #ifndef BOOST_CONTRACT_DISABLE_THREADS
+            return already_locked();
+        #else
+            return already_unlocked();
+        #endif
+    }
+
+private:
+    void init_unlocked();
+    void init_locked();
+
+    void done_unlocked();
+    void done_locked();
+
+    static bool already_unlocked();
+    static bool already_locked();
+
+    struct mutex_tag;
+    typedef static_local_var<mutex_tag, boost::mutex> mutex;
+
+    struct checking_tag;
+    typedef static_local_var_init<checking_tag, bool, bool, false> flag;
+};
+
+#ifdef BOOST_MSVC
+    #pragma warning(pop)
+#endif
+
+} } } // namespace
+
+#ifdef BOOST_CONTRACT_HEADER_ONLY
+    #include <boost/contract/detail/inlined/detail/checking.hpp>
+#endif
+
+#endif // #include guard
+

install/boost_1_75_0/include/boost/contract/detail/condition/cond_base.hpp

@@ -0,0 +1,153 @@
+
+#ifndef BOOST_CONTRACT_DETAIL_COND_BASE_HPP_
+#define BOOST_CONTRACT_DETAIL_COND_BASE_HPP_
+
+// Copyright (C) 2008-2018 Lorenzo Caminiti
+// Distributed under the Boost Software License, Version 1.0 (see accompanying
+// file LICENSE_1_0.txt or a copy at http://www.boost.org/LICENSE_1_0.txt).
+// See: http://www.boost.org/doc/libs/release/libs/contract/doc/html/index.html
+
+// NOTE: It seemed not possible to implement this library without inheritance
+// here because some sort of base type needs to be used to hold contract objects
+// in instances of boost::contract::check while polymorphically calling
+// init and destructor functions to check contracts at entry and exit. This
+// could be possible without inheritance only if boost::contract::check was made
+// a template type but that would complicate user code. In any case, early
+// experimentation with removing this base class and its virtual methods did not
+// seem to reduce compilation and/or run time.
+
+#include <boost/contract/core/exception.hpp>
+#include <boost/contract/core/config.hpp>
+#if     !defined(BOOST_CONTRACT_NO_PRECONDITIONS) || \
+        !defined(BOOST_CONTRACT_NO_OLDS) || \
+        !defined(BOOST_CONTRACT_NO_EXEPTS)
+    #include <boost/function.hpp>
+#endif
+#include <boost/noncopyable.hpp>
+#ifndef BOOST_CONTRACT_ON_MISSING_CHECK_DECL
+    #include <boost/assert.hpp>
+#endif
+#include <boost/config.hpp>
+
+namespace boost { namespace contract { namespace detail {
+
+class cond_base : // Base to hold all contract objects for RAII.
+    private boost::noncopyable // Avoid copying possible user's ftor captures.
+{
+public:
+    explicit cond_base(boost::contract::from from) :
+          BOOST_CONTRACT_ERROR_missing_check_object_declaration(false)
+        , init_asserted_(false)
+        #ifndef BOOST_CONTRACT_NO_CONDITIONS
+            , from_(from)
+            , failed_(false)
+        #endif
+    {}
+    
+    // Can override for checking on exit, but should call assert_initialized().
+    virtual ~cond_base() BOOST_NOEXCEPT_IF(false) {
+        // Catch error (but later) even if overrides miss assert_initialized().
+        if(!init_asserted_) assert_initialized();
+    }
+
+    void initialize() { // Must be called by owner ctor (i.e., check class).
+        BOOST_CONTRACT_ERROR_missing_check_object_declaration = true;
+        this->init(); // So all inits (pre, old, post) done after owner decl.
+    }
+    
+    #ifndef BOOST_CONTRACT_NO_PRECONDITIONS
+        template<typename F>
+        void set_pre(F const& f) { pre_ = f; }
+    #endif
+
+    #ifndef BOOST_CONTRACT_NO_OLDS
+        template<typename F>
+        void set_old(F const& f) { old_ = f; }
+    #endif
+
+    #ifndef BOOST_CONTRACT_NO_EXCEPTS
+        template<typename F>
+        void set_except(F const& f) { except_ = f; }
+    #endif
+
+protected:
+    void assert_initialized() { // Derived dtors must assert this at entry.
+        init_asserted_ = true;
+        #ifdef BOOST_CONTRACT_ON_MISSING_CHECK_DECL
+            if(!BOOST_CONTRACT_ERROR_missing_check_object_declaration) {
+                BOOST_CONTRACT_ON_MISSING_CHECK_DECL;
+            }
+        #else
+            // Cannot use a macro instead of this ERROR_... directly here
+            // because assert will not expand it in the error message.
+            BOOST_ASSERT(BOOST_CONTRACT_ERROR_missing_check_object_declaration);
+        #endif
+    }
+    
+    virtual void init() {} // Override for checking on entry.
+    
+    // Return true if actually checked calling user ftor.
+    #ifndef BOOST_CONTRACT_NO_PRECONDITIONS
+        bool check_pre(bool throw_on_failure = false) {
+            if(failed()) return true;
+            try { if(pre_) pre_(); else return false; }
+            catch(...) {
+                // Subcontracted pre must throw on failure (instead of
+                // calling failure handler) so to be checked in logic-or.
+                if(throw_on_failure) throw;
+                fail(&boost::contract::precondition_failure);
+            }
+            return true;
+        }
+    #endif
+
+    #ifndef BOOST_CONTRACT_NO_OLDS
+        void copy_old() {
+            if(failed()) return;
+            try { if(old_) old_(); }
+            catch(...) { fail(&boost::contract::old_failure); }
+        }
+    #endif
+
+    #ifndef BOOST_CONTRACT_NO_EXCEPTS
+        void check_except() {
+            if(failed()) return;
+            try { if(except_) except_(); }
+            catch(...) { fail(&boost::contract::except_failure); }
+        }
+    #endif
+    
+    #ifndef BOOST_CONTRACT_NO_CONDITIONS
+        void fail(void (*h)(boost::contract::from)) {
+            failed(true);
+            if(h) h(from_);
+        }
+    
+        // Virtual so overriding pub func can use virtual_::failed_ instead.
+        virtual bool failed() const { return failed_; }
+        virtual void failed(bool value) { failed_ = value; }
+    #endif
+
+private:
+    bool BOOST_CONTRACT_ERROR_missing_check_object_declaration;
+    bool init_asserted_; // Avoid throwing twice from dtors (undef behavior).
+    #ifndef BOOST_CONTRACT_NO_CONDITIONS
+        boost::contract::from from_;
+        bool failed_;
+    #endif
+    // Following use Boost.Function to handle also lambdas, binds, etc.
+    #ifndef BOOST_CONTRACT_NO_PRECONDITIONS
+        boost::function<void ()> pre_;
+    #endif
+    #ifndef BOOST_CONTRACT_NO_OLDS
+        boost::function<void ()> old_;
+    #endif
+    #ifndef BOOST_CONTRACT_NO_EXCEPTS
+        boost::function<void ()> except_;
+    #endif
+};
+
+} } } // namespace
+
+#endif // #include guard
+

install/boost_1_75_0/include/boost/contract/detail/condition/cond_inv.hpp

@@ -0,0 +1,232 @@
+
+#ifndef BOOST_CONTRACT_DETAIL_COND_INV_HPP_
+#define BOOST_CONTRACT_DETAIL_COND_INV_HPP_
+
+// Copyright (C) 2008-2018 Lorenzo Caminiti
+// Distributed under the Boost Software License, Version 1.0 (see accompanying
+// file LICENSE_1_0.txt or a copy at http://www.boost.org/LICENSE_1_0.txt).
+// See: http://www.boost.org/doc/libs/release/libs/contract/doc/html/index.html
+
+#include <boost/contract/core/exception.hpp>
+#include <boost/contract/core/config.hpp>
+#include <boost/contract/detail/condition/cond_post.hpp>
+#ifndef BOOST_CONTRACT_NO_INVARIANTS
+    #include <boost/contract/core/access.hpp>
+    #include <boost/type_traits/add_pointer.hpp>
+    #include <boost/type_traits/is_volatile.hpp>
+    #include <boost/mpl/vector.hpp>
+    #include <boost/mpl/transform.hpp>
+    #include <boost/mpl/for_each.hpp>
+    #include <boost/mpl/copy_if.hpp>
+    #include <boost/mpl/eval_if.hpp>
+    #include <boost/mpl/not.hpp>
+    #include <boost/mpl/and.hpp>
+    #include <boost/mpl/placeholders.hpp>
+    #include <boost/utility/enable_if.hpp>
+    #ifndef BOOST_CONTRACT_PERMISSIVE
+        #include <boost/function_types/property_tags.hpp>
+        #include <boost/static_assert.hpp>
+    #endif
+#endif
+
+namespace boost { namespace contract { namespace detail {
+
+template<typename VR, class C>
+class cond_inv : public cond_post<VR> { // Non-copyable base.
+    #if     !defined(BOOST_CONTRACT_NO_INVARIANTS) && \
+            !defined(BOOST_CONTRACT_PERMISSIVE)
+        BOOST_STATIC_ASSERT_MSG(
+            (!boost::contract::access::has_static_invariant_f<
+                C, void, boost::mpl:: vector<>
+            >::value),
+            "static invariant member function cannot be mutable "
+            "(it must be static instead)"
+        );
+        BOOST_STATIC_ASSERT_MSG(
+            (!boost::contract::access::has_static_invariant_f<
+                C, void, boost::mpl::vector<>,
+                        boost::function_types::const_non_volatile
+            >::value),
+            "static invariant member function cannot be const qualified "
+            "(it must be static instead)"
+        );
+        BOOST_STATIC_ASSERT_MSG(
+            (!boost::contract::access::has_static_invariant_f<
+                C, void, boost::mpl::vector<>,
+                        boost::function_types::volatile_non_const
+            >::value),
+            "static invariant member function cannot be volatile qualified "
+            "(it must be static instead)"
+        );
+        BOOST_STATIC_ASSERT_MSG(
+            (!boost::contract::access::has_static_invariant_f<
+                C, void, boost::mpl::vector<>,
+                        boost::function_types::cv_qualified
+            >::value),
+            "static invariant member function cannot be const volatile "
+            "qualified (it must be static instead)"
+        );
+
+        BOOST_STATIC_ASSERT_MSG(
+            (!boost::contract::access::has_invariant_s<
+                C, void, boost::mpl::vector<>
+            >::value),
+            "non-static invariant member function cannot be static "
+            "(it must be either const or const volatile qualified instead)"
+        );
+        BOOST_STATIC_ASSERT_MSG(
+            (!boost::contract::access::has_invariant_f<
+                C, void, boost::mpl::vector<>,
+                        boost::function_types::non_cv
+            >::value),
+            "non-static invariant member function cannot be mutable "
+            "(it must be either const or const volatile qualified instead)"
+        );
+        BOOST_STATIC_ASSERT_MSG(
+            (!boost::contract::access::has_invariant_f<
+                C, void, boost::mpl::vector<>,
+                        boost::function_types::volatile_non_const
+            >::value),
+            "non-static invariant member function cannot be volatile qualified "
+            "(it must be const or const volatile qualified instead)"
+        );
+    #endif
+
+public:
+    // obj can be 0 for static member functions.
+    explicit cond_inv(boost::contract::from from, C* obj) :
+        cond_post<VR>(from)
+        #ifndef BOOST_CONTRACT_NO_CONDITIONS
+            , obj_(obj)
+        #endif
+    {}
+    
+protected:
+    #ifndef BOOST_CONTRACT_NO_ENTRY_INVARIANTS
+        void check_entry_inv() { check_inv(true, false, false); }
+        void check_entry_static_inv() { check_inv(true, true, false); }
+        void check_entry_all_inv() { check_inv(true, false, true); }
+    #endif
+    
+    #ifndef BOOST_CONTRACT_NO_EXIT_INVARIANTS
+        void check_exit_inv() { check_inv(false, false, false); }
+        void check_exit_static_inv() { check_inv(false, true, false); }
+        void check_exit_all_inv() { check_inv(false, false, true); }
+    #endif
+
+    #ifndef BOOST_CONTRACT_NO_CONDITIONS
+        C* object() { return obj_; }
+    #endif
+
+private:
+    #ifndef BOOST_CONTRACT_NO_INVARIANTS
+        // Static, cv, and const inv in that order as strongest qualifier first.
+        void check_inv(bool on_entry, bool static_only, bool const_and_cv) {
+            if(this->failed()) return;
+            try {
+                // Static members only check static inv.
+                check_static_inv<C>();
+                if(!static_only) {
+                    if(const_and_cv) {
+                        check_cv_inv<C>();
+                        check_const_inv<C>();
+                    } else if(boost::is_volatile<C>::value) {
+                        check_cv_inv<C>();
+                    } else {
+                        check_const_inv<C>();
+                    }
+                }
+            } catch(...) {
+                if(on_entry) {
+                    this->fail(&boost::contract::entry_invariant_failure);
+                } else this->fail(&boost::contract::exit_invariant_failure);
+            }
+        }
+        
+        template<class C_>
+        typename boost::disable_if<
+                boost::contract::access::has_const_invariant<C_> >::type
+        check_const_inv() {}
+        
+        template<class C_>
+        typename boost::enable_if<
+                boost::contract::access::has_const_invariant<C_> >::type
+        check_const_inv() { boost::contract::access::const_invariant(obj_); }
+        
+        template<class C_>
+        typename boost::disable_if<
+                boost::contract::access::has_cv_invariant<C_> >::type
+        check_cv_inv() {}
+
+        template<class C_>
+        typename boost::enable_if<
+                boost::contract::access::has_cv_invariant<C_> >::type
+        check_cv_inv() { boost::contract::access::cv_invariant(obj_); }
+        
+        template<class C_>
+        typename boost::disable_if<
+                boost::contract::access::has_static_invariant<C_> >::type
+        check_static_inv() {}
+        
+        template<class C_>
+        typename boost::enable_if<
+                boost::contract::access::has_static_invariant<C_> >::type
+        check_static_inv() {
+            // SFINAE HAS_STATIC_... returns true even when member is inherited
+            // so extra run-time check here (not the same for non static).
+            if(!inherited<boost::contract::access::has_static_invariant,
+                    boost::contract::access::static_invariant_addr>::apply()) {
+                boost::contract::access::static_invariant<C_>();
+            }
+        }
+
+        // Check if class's func is inherited from its base types or not.
+        template<template<class> class HasFunc, template<class> class FuncAddr>
+        struct inherited {
+            static bool apply() {
+                try {
+                    boost::mpl::for_each<
+                        // For now, no reason to deeply search inheritance tree
+                        // (SFINAE HAS_STATIC_... already fails in that case).
+                        typename boost::mpl::transform<
+                            typename boost::mpl::copy_if<
+                                typename boost::mpl::eval_if<boost::contract::
+                                        access::has_base_types<C>,
+                                    typename boost::contract::access::
+                                            base_types_of<C>
+                                ,
+                                    boost::mpl::vector<>
+                                >::type,
+                                HasFunc<boost::mpl::_1>
+                            >::type,
+                            boost::add_pointer<boost::mpl::_1>
+                        >::type
+                    >(compare_func_addr());
+                } catch(signal_equal const&) { return true; }
+                return false;
+            }
+
+        private:
+            class signal_equal {}; // Except. to stop for_each as soon as found.
+
+            struct compare_func_addr {
+                template<typename B>
+                void operator()(B*) {
+                    // Inherited func has same addr as in its base.
+                    if(FuncAddr<C>::apply() == FuncAddr<B>::apply()) {
+                        throw signal_equal();
+                    }
+                }
+            };
+        };
+    #endif
+
+    #ifndef BOOST_CONTRACT_NO_CONDITIONS
+        C* obj_;
+    #endif
+};
+
+} } } // namespace
+
+#endif // #include guard
+

install/boost_1_75_0/include/boost/contract/detail/condition/cond_post.hpp

@@ -0,0 +1,89 @@
+
+#ifndef BOOST_CONTRACT_DETAIL_COND_POST_HPP_
+#define BOOST_CONTRACT_DETAIL_COND_POST_HPP_
+
+// Copyright (C) 2008-2018 Lorenzo Caminiti
+// Distributed under the Boost Software License, Version 1.0 (see accompanying
+// file LICENSE_1_0.txt or a copy at http://www.boost.org/LICENSE_1_0.txt).
+// See: http://www.boost.org/doc/libs/release/libs/contract/doc/html/index.html
+
+#include <boost/contract/core/exception.hpp>
+#include <boost/contract/core/config.hpp>
+#include <boost/contract/detail/condition/cond_base.hpp>
+#include <boost/contract/detail/none.hpp>
+#ifndef BOOST_CONTRACT_NO_POSTCONDITIONS
+    #include <boost/contract/detail/type_traits/optional.hpp>
+    #include <boost/optional.hpp>
+    #include <boost/function.hpp>
+    #include <boost/type_traits/remove_reference.hpp>
+    #include <boost/mpl/if.hpp>
+    #include <boost/preprocessor/facilities/empty.hpp>
+#endif
+
+/* PRIVATE */
+
+#define BOOST_CONTRACT_DETAIL_COND_POST_DEF_( \
+        result_type, result_param, ftor_type, ftor_var, ftor_call) \
+    public: \
+        template<typename F> \
+        void set_post(F const& f) { ftor_var = f; } \
+    \
+    protected: \
+        void check_post(result_type const& result_param) { \
+            if(failed()) return; \
+            try { if(ftor_var) { ftor_call; } } \
+            catch(...) { fail(&boost::contract::postcondition_failure); } \
+        } \
+    \
+    private: \
+        boost::function<ftor_type> ftor_var; /* Boost.Func for lambdas, etc. */
+
+/* CODE */
+
+namespace boost { namespace contract { namespace detail {
+
+template<typename VR>
+class cond_post : public cond_base { // Non-copyable base.
+public:
+    explicit cond_post(boost::contract::from from) : cond_base(from) {}
+    
+    #ifndef BOOST_CONTRACT_NO_POSTCONDITIONS
+        private: typedef typename boost::mpl::if_<is_optional<VR>,
+            boost::optional<typename boost::remove_reference<typename
+                    optional_value_type<VR>::type>::type const&> const&
+        ,
+            VR const&
+        >::type r_type;
+
+        BOOST_CONTRACT_DETAIL_COND_POST_DEF_(
+            r_type,
+            r,
+            void (r_type),
+            // Won't raise this error if NO_POST (for optimization).
+            BOOST_CONTRACT_ERROR_postcondition_result_parameter_required,
+            BOOST_CONTRACT_ERROR_postcondition_result_parameter_required(r)
+        )
+    #endif
+};
+
+template<>
+class cond_post<none> : public cond_base { // Non-copyable base.
+public:
+    explicit cond_post(boost::contract::from from) : cond_base(from) {}
+    
+    #ifndef BOOST_CONTRACT_NO_POSTCONDITIONS
+        BOOST_CONTRACT_DETAIL_COND_POST_DEF_(
+            none,
+            /* r */ BOOST_PP_EMPTY(),
+            void (),
+            // Won't raise this error if NO_POST (for optimization).
+            BOOST_CONTRACT_ERROR_postcondition_result_parameter_not_allowed,
+            BOOST_CONTRACT_ERROR_postcondition_result_parameter_not_allowed()
+        )
+    #endif
+};
+
+} } } // namespace
+
+#endif // #include guard
+

install/boost_1_75_0/include/boost/contract/detail/condition/cond_subcontracting.hpp

@@ -0,0 +1,475 @@
+
+#ifndef BOOST_CONTRACT_DETAIL_COND_SUBCONTRACTING_HPP_
+#define BOOST_CONTRACT_DETAIL_COND_SUBCONTRACTING_HPP_
+
+// Copyright (C) 2008-2018 Lorenzo Caminiti
+// Distributed under the Boost Software License, Version 1.0 (see accompanying
+// file LICENSE_1_0.txt or a copy at http://www.boost.org/LICENSE_1_0.txt).
+// See: http://www.boost.org/doc/libs/release/libs/contract/doc/html/index.html
+
+#include <boost/contract/core/config.hpp>
+#if     !defined(BOOST_CONTRACT_NO_PRECONDITIONS) || \
+        !defined(BOOST_CONTRACT_NO_POSTCONDITIONS) || \
+        !defined(BOOST_CONTRACT_NO_EXCEPTS)
+    #include <boost/contract/core/exception.hpp>
+#endif
+#include <boost/contract/detail/condition/cond_inv.hpp>
+#include <boost/contract/detail/decl.hpp>
+#include <boost/contract/detail/tvariadic.hpp>
+#ifndef BOOST_CONTRACT_NO_CONDITIONS
+    #include <boost/contract/core/virtual.hpp>
+    #include <boost/contract/core/access.hpp>
+    #include <boost/contract/detail/type_traits/optional.hpp>
+    #include <boost/contract/detail/type_traits/member_function_types.hpp>
+    #include <boost/contract/detail/debug.hpp>
+    #include <boost/contract/detail/none.hpp>
+    #include <boost/contract/detail/name.hpp>
+    #include <boost/type_traits/add_pointer.hpp>
+    #include <boost/mpl/fold.hpp>
+    #include <boost/mpl/contains.hpp>
+    #include <boost/mpl/empty.hpp>
+    #include <boost/mpl/push_back.hpp>
+    #include <boost/mpl/eval_if.hpp>
+    #include <boost/mpl/identity.hpp>
+    #include <boost/mpl/placeholders.hpp>
+    #ifndef BOOST_CONTRACT_PERMISSIVE
+        #include <boost/type_traits/is_same.hpp>
+        #include <boost/mpl/or.hpp>
+        #include <boost/mpl/not.hpp>
+        #include <boost/static_assert.hpp>
+    #endif
+    #include <boost/preprocessor/punctuation/comma_if.hpp>
+    #include <boost/config.hpp>
+#endif
+#include <boost/mpl/vector.hpp>
+#if     !defined(BOOST_CONTRACT_NO_INVARIANTS) || \
+        !defined(BOOST_CONTRACT_NO_POSTCONDITIONS) || \
+        !defined(BOOST_CONTRACT_NO_EXCEPTS)
+    #include <boost/mpl/for_each.hpp>
+#endif
+#ifndef BOOST_CONTRACT_NO_PRECONDITIONS
+    #include <boost/mpl/pop_front.hpp>
+    #include <boost/mpl/front.hpp>
+#endif
+#if     !defined(BOOST_CONTRACT_NO_POSTCONDITIONS) || \
+        !defined(BOSOT_CONTRACT_NO_EXCEPTS)
+    #include <boost/any.hpp>
+    #include <boost/optional.hpp>
+    #include <boost/type_traits/remove_reference.hpp>
+    #include <boost/utility/enable_if.hpp>
+    #include <typeinfo>
+#endif
+
+namespace boost { namespace contract { namespace detail {
+
+namespace cond_subcontracting_ {
+    // Exception signals (must not inherit).
+    class signal_no_error {};
+    class signal_not_checked {};
+}
+
+// O, VR, F, and Args-i can be none types (but C cannot).
+BOOST_CONTRACT_DETAIL_DECL_DETAIL_COND_SUBCONTRACTING_Z(1,
+        /* is_friend = */ 0, O, VR, F, C, Args) : public cond_inv<VR, C>
+{ // Non-copyable base.
+    #ifndef BOOST_CONTRACT_NO_CONDITIONS
+        template<class Class, typename Result = boost::mpl::vector<> >
+        class overridden_bases_of {
+            struct search_bases {
+                typedef typename boost::mpl::fold<
+                    typename boost::contract::access::base_types_of<Class>::
+                            type,
+                    Result,
+                    // Fold: _1 = result, _2 = current base from base_types.
+                    boost::mpl::eval_if<boost::mpl::contains<boost::mpl::_1,
+                            boost::add_pointer<boost::mpl::_2> >,
+                        boost::mpl::_1 // Base in result, do not add it again.
+                    ,
+                        boost::mpl::eval_if<
+                            typename O::template BOOST_CONTRACT_DETAIL_NAME1(
+                                    has_member_function)<
+                                boost::mpl::_2,
+                                typename member_function_types<C, F>::
+                                        result_type,
+                                typename member_function_types<C, F>::
+                                        virtual_argument_types,
+                                typename member_function_types<C, F>::
+                                        property_tag
+                            >
+                        ,
+                            boost::mpl::push_back<
+                                overridden_bases_of<boost::mpl::_2,
+                                        boost::mpl::_1>,
+                                // Bases as * since for_each constructs them.
+                                boost::add_pointer<boost::mpl::_2>
+                            >
+                        ,
+                            overridden_bases_of<boost::mpl::_2, boost::mpl::_1>
+                        >
+                    >
+                >::type type;
+            };
+        public:
+            typedef typename boost::mpl::eval_if<
+                    boost::contract::access::has_base_types<Class>,
+                search_bases
+            ,
+                boost::mpl::identity<Result> // Return result (stop recursion).
+            >::type type;
+        };
+        
+        typedef typename boost::mpl::eval_if<boost::is_same<O, none>,
+            boost::mpl::vector<>
+        ,
+            overridden_bases_of<C>
+        >::type overridden_bases;
+
+        #ifndef BOOST_CONTRACT_PERMISSIVE
+            BOOST_STATIC_ASSERT_MSG(
+                (boost::mpl::or_<
+                    boost::is_same<O, none>,
+                    boost::mpl::not_<boost::mpl::empty<overridden_bases> >
+                >::value),
+                "subcontracting function specified as 'override' but does not "
+                "override any contracted member function"
+            );
+        #endif
+    #else
+        typedef boost::mpl::vector<> overridden_bases;
+    #endif
+
+public:
+    explicit cond_subcontracting(
+        boost::contract::from from,
+        boost::contract::virtual_* v,
+        C* obj,
+        VR&
+        #ifndef BOOST_CONTRACT_NO_POSTCONDITIONS // Avoid unused param warning.
+            r
+        #endif
+        BOOST_CONTRACT_DETAIL_TVARIADIC_COMMA(BOOST_CONTRACT_MAX_ARGS)
+        BOOST_CONTRACT_DETAIL_TVARIADIC_FPARAMS_Z(1,
+                BOOST_CONTRACT_MAX_ARGS, Args, &, args)
+    ) :
+        cond_inv<VR, C>(from, obj)
+        #ifndef BOOST_CONTRACT_NO_POSTCONDITIONS
+            , r_(r)
+        #endif
+        #ifndef BOOST_CONTRACT_NO_CONDITIONS
+            BOOST_CONTRACT_DETAIL_TVARIADIC_COMMA(BOOST_CONTRACT_MAX_ARGS)
+            BOOST_CONTRACT_DETAIL_TVARIADIC_TUPLE_INIT_Z(1,
+                    BOOST_CONTRACT_MAX_ARGS, args_, args)
+        #endif
+    {
+        #ifndef BOOST_CONTRACT_NO_CONDITIONS
+            if(v) {
+                base_call_ = true;
+                v_ = v; // Invariant: v_ never null if base_call_.
+                BOOST_CONTRACT_DETAIL_DEBUG(v_);
+            } else {
+                base_call_ = false;
+                if(!boost::mpl::empty<overridden_bases>::value) {
+                    v_ = new boost::contract::virtual_(
+                            boost::contract::virtual_::no_action);
+                    #ifndef BOOST_CONTRACT_NO_POSTCONDITIONS
+                        v_->result_ptr_ = &r_;
+                        v_->result_type_name_ = typeid(VR).name();
+                        v_->result_optional_ = is_optional<VR>::value;
+                    #endif
+                } else v_ = 0;
+            }
+        #endif
+    }
+
+    #ifndef BOOST_CONTRACT_NO_CONDITIONS
+        virtual ~cond_subcontracting() BOOST_NOEXCEPT_IF(false) {
+            if(!base_call_) delete v_;
+        }
+    #endif
+
+protected:
+    #ifndef BOOST_CONTRACT_NO_OLDS
+        void init_subcontracted_old() {
+            // Old values of overloaded func on stack (so no `f` param here).
+            exec_and(boost::contract::virtual_::push_old_init_copy);
+        }
+    #endif
+    
+    #ifndef BOOST_CONTRACT_NO_ENTRY_INVARIANTS
+        void check_subcontracted_entry_inv() {
+            exec_and(boost::contract::virtual_::check_entry_inv,
+                    &cond_subcontracting::check_entry_inv);
+        }
+    #endif
+    
+    #ifndef BOOST_CONTRACT_NO_PRECONDITIONS
+        void check_subcontracted_pre() {
+            exec_or(
+                boost::contract::virtual_::check_pre,
+                &cond_subcontracting::check_pre,
+                &boost::contract::precondition_failure
+            );
+        }
+    #endif
+
+    #ifndef BOOST_CONTRACT_NO_OLDS
+        void copy_subcontracted_old() {
+            exec_and(boost::contract::virtual_::call_old_ftor,
+                    &cond_subcontracting::copy_virtual_old);
+        }
+    #endif
+
+    #ifndef BOOST_CONTRACT_NO_EXIT_INVARIANTS
+        void check_subcontracted_exit_inv() {
+            exec_and(boost::contract::virtual_::check_exit_inv,
+                    &cond_subcontracting::check_exit_inv);
+        }
+    #endif
+
+    #ifndef BOOST_CONTRACT_NO_POSTCONDITIONS
+        void check_subcontracted_post() {
+            exec_and(boost::contract::virtual_::check_post,
+                    &cond_subcontracting::check_virtual_post);
+        }
+    #endif
+
+    #ifndef BOOST_CONTRACT_NO_EXCEPTS
+        void check_subcontracted_except() {
+            exec_and(boost::contract::virtual_::check_except,
+                    &cond_subcontracting::check_virtual_except);
+        }
+    #endif
+
+    #ifndef BOOST_CONTRACT_NO_CONDITIONS
+        bool base_call() const { return base_call_; }
+
+        bool failed() const /* override */ {
+            if(v_) return v_->failed_;
+            else return cond_base::failed();
+        }
+
+        void failed(bool value) /* override */ {
+            if(v_) v_->failed_ = value;
+            else cond_base::failed(value);
+        }
+    #endif
+
+private:
+    #ifndef BOOST_CONTRACT_NO_OLDS
+        void copy_virtual_old() {
+            boost::contract::virtual_::action_enum a;
+            if(base_call_) {
+                a = v_->action_;
+                v_->action_ = boost::contract::virtual_::push_old_ftor_copy;
+            }
+            this->copy_old();
+            if(base_call_) v_->action_ = a;
+        }
+            
+        void pop_base_old() {
+            if(base_call_) {
+                boost::contract::virtual_::action_enum a = v_->action_;
+                v_->action_ = boost::contract::virtual_::pop_old_ftor_copy;
+                this->copy_old();
+                v_->action_ = a;
+            } // Else, do nothing (for base calls only).
+        }
+    #endif
+
+    #ifndef BOOST_CONTRACT_NO_POSTCONDITIONS
+        void check_virtual_post() {
+            pop_base_old();
+            typedef typename boost::remove_reference<typename
+                    optional_value_type<VR>::type>::type r_type;
+            boost::optional<r_type const&> r; // No result copy in this code.
+            if(!base_call_) r = optional_get(r_);
+            else if(v_->result_optional_) {
+                try {
+                    r = **boost::any_cast<boost::optional<r_type>*>(
+                            v_->result_ptr_);
+                } catch(boost::bad_any_cast const&) {
+                    try { // Handle optional<...&>.
+                        r = **boost::any_cast<boost::optional<r_type&>*>(
+                                v_->result_ptr_);
+                    } catch(boost::bad_any_cast const&) {
+                        try {
+                            throw boost::contract::bad_virtual_result_cast(v_->
+                                    result_type_name_, typeid(r_type).name());
+                        } catch(...) {
+                            this->fail(&boost::contract::postcondition_failure);
+                        }
+                    }
+                }
+            } else {
+                try {
+                    r = *boost::any_cast<r_type*>(v_->result_ptr_);
+                } catch(boost::bad_any_cast const&) {
+                    try {
+                        throw boost::contract::bad_virtual_result_cast(
+                                v_->result_type_name_, typeid(r_type).name());
+                    } catch(...) {
+                        this->fail(&boost::contract::postcondition_failure);
+                    }
+                }
+            }
+            check_virtual_post_with_result<VR>(r);
+        }
+
+        template<typename R_, typename Result>
+        typename boost::enable_if<is_optional<R_> >::type
+        check_virtual_post_with_result(Result const& r) {
+            this->check_post(r);
+        }
+        
+        template<typename R_, typename Result>
+        typename boost::disable_if<is_optional<R_> >::type
+        check_virtual_post_with_result(Result const& r) {
+            BOOST_CONTRACT_DETAIL_DEBUG(r);
+            this->check_post(*r);
+        }
+    #endif
+    
+    #ifndef BOOST_CONTRACT_NO_EXCEPTS
+        void check_virtual_except() {
+            pop_base_old();
+            this->check_except();
+        }
+    #endif
+
+    #if     !defined(BOOST_CONTRACT_NO_INVARIANTS) || \
+            !defined(BOOST_CONTRACT_NO_POSTCONDITIONS) || \
+            !defined(BOOST_CONTRACT_NO_EXCEPTS)
+        void exec_and( // Execute action in short-circuit logic-and with bases.
+            boost::contract::virtual_::action_enum a,
+            void (cond_subcontracting::* f)() = 0
+        ) {
+            if(failed()) return;
+            if(!base_call_ || v_->action_ == a) {
+                if(!base_call_ && v_) {
+                    v_->action_ = a;
+                    boost::mpl::for_each<overridden_bases>(call_base(*this));
+                }
+                if(f) (this->*f)();
+                if(base_call_) {
+                    throw cond_subcontracting_::signal_no_error();
+                }
+            }
+        }
+    #endif
+
+    #ifndef BOOST_CONTRACT_NO_PRECONDITIONS
+        void exec_or( // Execute action in short-circuit logic-or with bases.
+            boost::contract::virtual_::action_enum a,
+            bool (cond_subcontracting::* f)(bool) = 0,
+            void (*h)(boost::contract::from) = 0
+        ) {
+            if(failed()) return;
+            if(!base_call_ || v_->action_ == a) {
+                if(!base_call_ && v_) {
+                    v_->action_ = a;
+                    try { 
+                        exec_or_bases<overridden_bases>();
+                        return; // A base checked with no error (done).
+                    } catch(...) {
+                        bool checked =  f ? (this->*f)(
+                                /* throw_on_failure = */ false) : false;
+                        if(!checked) {
+                            try { throw; } // Report latest exception found.
+                            catch(...) { this->fail(h); }
+                        }
+                        return; // Checked and no exception (done).
+                    }
+                }
+                bool checked = f ?
+                        (this->*f)(/* throw_on_failure = */ base_call_) : false;
+                if(base_call_) {
+                    if(!checked) {
+                        throw cond_subcontracting_::signal_not_checked();
+                    }
+                    throw cond_subcontracting_::signal_no_error();
+                }
+            }
+        }
+        
+        template<typename Bases>
+        typename boost::enable_if<boost::mpl::empty<Bases>, bool>::type
+        exec_or_bases() { return false; }
+
+        template<typename Bases>
+        typename boost::disable_if<boost::mpl::empty<Bases>, bool>::type
+        exec_or_bases() {
+            if(boost::mpl::empty<Bases>::value) return false;
+            try {
+                call_base(*this)(typename boost::mpl::front<Bases>::type());
+            } catch(cond_subcontracting_::signal_not_checked const&) {
+                return exec_or_bases<
+                        typename boost::mpl::pop_front<Bases>::type>();
+            } catch(...) {
+                bool checked = false;
+                try {
+                    checked = exec_or_bases<
+                            typename boost::mpl::pop_front<Bases>::type>();
+                } catch(...) { checked = false; }
+                if(!checked) throw;
+            }
+            return true;
+        }
+    #endif
+    
+    #ifndef BOOST_CONTRACT_NO_CONDITIONS
+        class call_base { // Copyable (as &).
+        public:
+            explicit call_base(cond_subcontracting& me) : me_(me) {}
+
+            template<class B>
+            void operator()(B*) {
+                BOOST_CONTRACT_DETAIL_DEBUG(me_.object());
+                BOOST_CONTRACT_DETAIL_DEBUG(me_.v_);
+                BOOST_CONTRACT_DETAIL_DEBUG(me_.v_->action_ !=
+                        boost::contract::virtual_::no_action);
+                try {
+                    call<B>(BOOST_CONTRACT_DETAIL_TVARIADIC_TUPLE_INDEXES_OF(
+                            Args));
+                } catch(cond_subcontracting_::signal_no_error const&) {
+                    // No error (do not throw).
+                }
+            }
+
+        private:
+            template<
+                class B
+                // Can't use TVARIADIC_COMMA here.
+                BOOST_PP_COMMA_IF(BOOST_CONTRACT_DETAIL_TVARIADIC)
+                BOOST_CONTRACT_DETAIL_TVARIADIC_TUPLE_INDEXES_TPARAM(I)
+            >
+            void call(
+                    BOOST_CONTRACT_DETAIL_TVARIADIC_TUPLE_INDEXES_FPARAM(I)) {
+                O::template BOOST_CONTRACT_DETAIL_NAME1(call_base)<B>(
+                    me_.v_,
+                    me_.object()
+                    BOOST_CONTRACT_DETAIL_TVARIADIC_COMMA(
+                            BOOST_CONTRACT_MAX_ARGS)
+                    BOOST_CONTRACT_DETAIL_TVARIADIC_TUPLE_ELEMS_Z(1,
+                            BOOST_CONTRACT_MAX_ARGS, I, me_.args_)
+                );
+            }
+            
+            cond_subcontracting& me_;
+        };
+    #endif
+
+    #ifndef BOOST_CONTRACT_NO_POSTCONDITIONS
+        VR& r_;
+    #endif
+    #ifndef BOOST_CONTRACT_NO_CONDITIONS
+        boost::contract::virtual_* v_;
+        bool base_call_;
+        BOOST_CONTRACT_DETAIL_TVARIADIC_TUPLE_Z(1,
+                BOOST_CONTRACT_MAX_ARGS, Args, &, args_)
+    #endif
+};
+
+} } } // namespace
+
+#endif // #include guard
+

install/boost_1_75_0/include/boost/contract/detail/config.hpp

@@ -0,0 +1,26 @@
+
+#ifndef BOOST_CONTRACT_DETAIL_CONFIG_HPP_
+#define BOOST_CONTRACT_DETAIL_CONFIG_HPP_
+
+// Copyright (C) 2008-2018 Lorenzo Caminiti
+// Distributed under the Boost Software License, Version 1.0 (see accompanying
+// file LICENSE_1_0.txt or a copy at http://www.boost.org/LICENSE_1_0.txt).
+// See: http://www.boost.org/doc/libs/release/libs/contract/doc/html/index.html
+
+#include <boost/preprocessor/cat.hpp>
+
+// Turn off BOOST_ASSERT(...) in lib's implementation (always on by default).
+// BOOST_CONTRACT_DETAIL_NDEBUG
+
+#ifndef BOOST_CONTRACT_DETAIL_NAME_INFIX
+    // Do not use underscore "_" to avoid generating reserved names with "__".
+    #define BOOST_CONTRACT_DETAIL_NAME_INFIX X
+#endif
+
+#ifndef BOOST_CONTRACT_DETAIL_NAME_PREFIX
+    #define BOOST_CONTRACT_DETAIL_NAME_PREFIX \
+        BOOST_PP_CAT(boost_contract_detail, BOOST_CONTRACT_DETAIL_NAME_INFIX)
+#endif
+
+#endif // #include guard
+

install/boost_1_75_0/include/boost/contract/detail/debug.hpp

@@ -0,0 +1,20 @@
+
+#ifndef BOOST_CONTRACT_DETAIL_DEBUG_HPP_
+#define BOOST_CONTRACT_DETAIL_DEBUG_HPP_
+
+// Copyright (C) 2008-2018 Lorenzo Caminiti
+// Distributed under the Boost Software License, Version 1.0 (see accompanying
+// file LICENSE_1_0.txt or a copy at http://www.boost.org/LICENSE_1_0.txt).
+// See: http://www.boost.org/doc/libs/release/libs/contract/doc/html/index.html
+
+// Usually, never #defined (so "debug" assertions always in code).
+#ifdef BOOST_CONTRACT_DETAIL_NDEBUG
+    #define BOOST_CONTRACT_DETAIL_DEBUG(cond) /* nothing */
+#else
+    #include <boost/assert.hpp>
+    // Extra parenthesis around BOOST_ASSERT to be safe because its is a macro.
+    #define BOOST_CONTRACT_DETAIL_DEBUG(cond) (BOOST_ASSERT(cond))
+#endif
+
+#endif // #include guard
+

install/boost_1_75_0/include/boost/contract/detail/decl.hpp

@@ -0,0 +1,129 @@
+
+#ifndef BOOST_CONTRACT_DETAIL_DECL_HPP_
+#define BOOST_CONTRACT_DETAIL_DECL_HPP_
+
+// Copyright (C) 2008-2018 Lorenzo Caminiti
+// Distributed under the Boost Software License, Version 1.0 (see accompanying
+// file LICENSE_1_0.txt or a copy at http://www.boost.org/LICENSE_1_0.txt).
+// See: http://www.boost.org/doc/libs/release/libs/contract/doc/html/index.html
+
+// Cannot include core/*.hpp other than config.hpp here (avoid circular incl).
+#include <boost/contract/detail/tvariadic.hpp>
+#if !BOOST_CONTRACT_DETAIL_TVARIADIC
+    #include <boost/contract/core/config.hpp>
+    #include <boost/preprocessor/repetition/repeat.hpp>
+    #include <boost/preprocessor/tuple/elem.hpp>
+    #include <boost/preprocessor/arithmetic/inc.hpp>
+#endif
+#include <boost/preprocessor/control/expr_iif.hpp>
+#include <boost/preprocessor/control/iif.hpp>
+#include <boost/preprocessor/punctuation/comma_if.hpp>
+
+/* PUBLIC */
+
+#define BOOST_CONTRACT_DETAIL_DECL_OVERRIDING_PUBLIC_FUNCTION_Z(z, \
+    arity, is_friend, has_result, \
+    O, VR, F, C, Args, \
+    v, r, f, obj, args \
+) \
+    template< \
+        class O \
+        BOOST_PP_COMMA_IF(has_result) \
+        BOOST_PP_EXPR_IIF(has_result, typename VR) \
+        , typename F \
+        , class C \
+        BOOST_CONTRACT_DETAIL_TVARIADIC_COMMA(arity) \
+        BOOST_CONTRACT_DETAIL_TVARIADIC_TPARAMS_Z(z, arity, Args) \
+    > \
+    BOOST_PP_EXPR_IIF(is_friend, friend) \
+    boost::contract::specify_precondition_old_postcondition_except< \
+            BOOST_PP_EXPR_IIF(has_result, VR)> \
+    /* no boost::contract:: here for friends (otherwise need fwd decl) */ \
+    public_function( \
+        boost::contract::virtual_* v \
+        BOOST_PP_COMMA_IF(has_result) \
+        BOOST_PP_EXPR_IIF(has_result, VR& r) \
+        , F f \
+        , C* obj \
+        BOOST_CONTRACT_DETAIL_TVARIADIC_COMMA(arity) \
+        BOOST_CONTRACT_DETAIL_TVARIADIC_FPARAMS_Z(z, arity, Args, &, args) \
+    )
+
+#if BOOST_CONTRACT_DETAIL_TVARIADIC
+    #define BOOST_CONTRACT_DETAIL_DECL_FRIEND_OVERRIDING_PUBLIC_FUNCTIONS_Z(z, \
+        O, VR, F, C, Args, \
+        v, r, f, obj, args \
+    ) \
+        BOOST_CONTRACT_DETAIL_DECL_OVERRIDING_PUBLIC_FUNCTION_Z(z, \
+            ~, /* is_friend = */ 1, /* has_result = */ 0, \
+            O, VR, F, C, Args, v, r, f, obj, args \
+        ); \
+        BOOST_CONTRACT_DETAIL_DECL_OVERRIDING_PUBLIC_FUNCTION_Z(z, \
+            ~, /* is_friend = */ 1, /* has_result = */ 1, \
+            O, VR, F, C, Args, v, r, f, obj, args \
+        );
+#else
+    /* PRIVATE */
+    #define BOOST_CONTRACT_DETAIL_DECL_FRIEND_OVERRIDING_PUBLIC_FUNCTION_( \
+            z, n, result_O_R_F_C_Args_v_r_f_obj_args) \
+        BOOST_CONTRACT_DETAIL_DECL_OVERRIDING_PUBLIC_FUNCTION_Z(z, \
+            /* arity = */ n, \
+            /* is_friend = */ 1, \
+            BOOST_PP_TUPLE_ELEM(11, 0, result_O_R_F_C_Args_v_r_f_obj_args), \
+            BOOST_PP_TUPLE_ELEM(11, 1, result_O_R_F_C_Args_v_r_f_obj_args), \
+            BOOST_PP_TUPLE_ELEM(11, 2, result_O_R_F_C_Args_v_r_f_obj_args), \
+            BOOST_PP_TUPLE_ELEM(11, 3, result_O_R_F_C_Args_v_r_f_obj_args), \
+            BOOST_PP_TUPLE_ELEM(11, 4, result_O_R_F_C_Args_v_r_f_obj_args), \
+            BOOST_PP_TUPLE_ELEM(11, 5, result_O_R_F_C_Args_v_r_f_obj_args), \
+            BOOST_PP_TUPLE_ELEM(11, 6, result_O_R_F_C_Args_v_r_f_obj_args), \
+            BOOST_PP_TUPLE_ELEM(11, 7, result_O_R_F_C_Args_v_r_f_obj_args), \
+            BOOST_PP_TUPLE_ELEM(11, 8, result_O_R_F_C_Args_v_r_f_obj_args), \
+            BOOST_PP_TUPLE_ELEM(11, 9, result_O_R_F_C_Args_v_r_f_obj_args), \
+            BOOST_PP_TUPLE_ELEM(11, 10, result_O_R_F_C_Args_v_r_f_obj_args) \
+        );
+
+    /* PUBLIC */
+    #define BOOST_CONTRACT_DETAIL_DECL_FRIEND_OVERRIDING_PUBLIC_FUNCTIONS_Z(z, \
+        O, VR, F, C, Args, \
+        v, r, f, obj, args \
+    ) \
+        BOOST_PP_REPEAT_ ## z( \
+            BOOST_PP_INC(BOOST_CONTRACT_MAX_ARGS), \
+            BOOST_CONTRACT_DETAIL_DECL_FRIEND_OVERRIDING_PUBLIC_FUNCTION_, \
+            (/* has_result = */ 0, O, VR, F, C, Args, v, r, f, obj, args) \
+        ) \
+        BOOST_PP_REPEAT_ ## z( \
+            BOOST_PP_INC(BOOST_CONTRACT_MAX_ARGS), \
+            BOOST_CONTRACT_DETAIL_DECL_FRIEND_OVERRIDING_PUBLIC_FUNCTION_, \
+            (/* has_result = */ 1, O, VR, F, C, Args, v, r, f, obj, args) \
+        )
+#endif
+
+#define BOOST_CONTRACT_DETAIL_DECL_DETAIL_COND_SUBCONTRACTING_Z( \
+        z, is_friend, O, VR, F, C, Args) \
+    template< \
+        class O, typename VR, typename F, class C \
+        BOOST_CONTRACT_DETAIL_TVARIADIC_COMMA(BOOST_CONTRACT_MAX_ARGS) \
+        BOOST_CONTRACT_DETAIL_TVARIADIC_TPARAMS_Z(z, \
+                BOOST_CONTRACT_MAX_ARGS, Args) \
+    > \
+    BOOST_PP_IIF(is_friend, \
+        friend class boost::contract::detail:: \
+    , \
+        class \
+    ) \
+    cond_subcontracting
+
+/* CODE */
+
+namespace boost {
+    namespace contract {
+        class virtual_;
+
+        template<typename VR = void>
+        class specify_precondition_old_postcondition_except;
+    }
+}
+    
+#endif // #include guard
+

install/boost_1_75_0/include/boost/contract/detail/declspec.hpp

@@ -0,0 +1,51 @@
+
+#ifndef BOOST_CONTRACT_DETAIL_DECLSPEC_HPP_
+#define BOOST_CONTRACT_DETAIL_DECLSPEC_HPP_
+
+// Copyright (C) 2008-2018 Lorenzo Caminiti
+// Distributed under the Boost Software License, Version 1.0 (see accompanying
+// file LICENSE_1_0.txt or a copy at http://www.boost.org/LICENSE_1_0.txt).
+// See: http://www.boost.org/doc/libs/release/libs/contract/doc/html/index.html
+
+// IMPORTANT: Indirectly included by contract_macro.hpp so trivial headers only.
+#include <boost/contract/core/config.hpp> // No compile-time overhead.
+#include <boost/config.hpp>
+
+/* PUBLIC */
+
+// IMPORTANT: In general, this library should always and only be compiled and
+// used as a shared library. Otherwise, lib's state won't be shared among
+// different user programs and user libraries. However, this library can be
+// safely compiled and used as a static or header-only library only when it is
+// being used by a single program unit (e.g., a single program with only
+// statically linked libraries that check contracts).
+
+#ifdef BOOST_CONTRACT_DYN_LINK
+    #ifdef BOOST_CONTRACT_SOURCE
+        #define BOOST_CONTRACT_DETAIL_DECLSPEC BOOST_SYMBOL_EXPORT
+    #else
+        #define BOOST_CONTRACT_DETAIL_DECLSPEC BOOST_SYMBOL_IMPORT
+    #endif
+#else
+    #define BOOST_CONTRACT_DETAIL_DECLSPEC /* nothing */
+#endif
+
+#ifdef BOOST_CONTRACT_HEADER_ONLY
+    #define BOOST_CONTRACT_DETAIL_DECLINLINE inline
+#else
+    #define BOOST_CONTRACT_DETAIL_DECLINLINE /* nothing */
+
+    // Automatically link this lib to correct build variant (for MSVC, etc.).
+    #if     !defined(BOOST_ALL_NO_LIB) && \
+            !defined(BOOST_CONTRACT_NO_LIB) && \
+            !defined(BOOST_CONTRACT_SOURCE)
+        #define BOOST_LIB_NAME boost_contract // This lib (static or shared).
+        #if defined(BOOST_ALL_DYN_LINK) || defined(BOOST_CONTRACT_DYN_LINK)
+            #define BOOST_DYN_LINK // This lib as shared.
+        #endif
+        #include <boost/config/auto_link.hpp> // Also #undef BOOST_LIB_NAME.
+    #endif
+#endif
+
+#endif // #include guard
+

install/boost_1_75_0/include/boost/contract/detail/exception.hpp

@@ -0,0 +1,31 @@
+
+#ifndef BOOST_CONTRACT_DETAIL_EXCEPTION_HPP_
+#define BOOST_CONTRACT_DETAIL_EXCEPTION_HPP_
+
+// Copyright (C) 2008-2019 Lorenzo Caminiti
+// Distributed under the Boost Software License, Version 1.0 (see accompanying
+// file LICENSE_1_0.txt or a copy at http://www.boost.org/LICENSE_1_0.txt).
+// See: http://www.boost.org/doc/libs/release/libs/contract/doc/html/index.html
+
+#include <boost/config.hpp>
+#include <exception>
+
+namespace boost { namespace contract { namespace detail {
+
+// Using this instead of std::uncaught_exception() because
+// std::uncaught_exception will be removed in C++20.
+inline bool uncaught_exception() BOOST_NOEXCEPT {
+    // Alternatively, this could just return `boost::core::uncaught_exceptions()
+    // > 0` but that emulates the exception count which is not needed by this
+    // lib (the implementation below is simpler and could be faster).
+    #ifdef __cpp_lib_uncaught_exceptions
+        return std::uncaught_exceptions() > 0;
+    #else
+        return std::uncaught_exception();
+    #endif
+}
+
+} } } // namespace
+
+#endif // #include guard
+

install/boost_1_75_0/include/boost/contract/detail/inlined.hpp

@@ -0,0 +1,15 @@
+
+#ifndef BOOST_CONTRACT_DETAIL_INLINED_HPP_
+#define BOOST_CONTRACT_DETAIL_INLINED_HPP_
+
+// Copyright (C) 2008-2018 Lorenzo Caminiti
+// Distributed under the Boost Software License, Version 1.0 (see accompanying
+// file LICENSE_1_0.txt or a copy at http://www.boost.org/LICENSE_1_0.txt).
+// See: http://www.boost.org/doc/libs/release/libs/contract/doc/html/index.html
+
+#include <boost/contract/detail/inlined/old.hpp>
+#include <boost/contract/detail/inlined/core/exception.hpp>
+#include <boost/contract/detail/inlined/detail/checking.hpp>
+
+#endif // #include guard
+

install/boost_1_75_0/include/boost/contract/detail/inlined/core/exception.hpp

@@ -0,0 +1,502 @@
+
+#ifndef BOOST_CONTRACT_DETAIL_INLINED_EXCEPTION_HPP_
+#define BOOST_CONTRACT_DETAIL_INLINED_EXCEPTION_HPP_
+
+// Copyright (C) 2008-2018 Lorenzo Caminiti
+// Distributed under the Boost Software License, Version 1.0 (see accompanying
+// file LICENSE_1_0.txt or a copy at http://www.boost.org/LICENSE_1_0.txt).
+// See: http://www.boost.org/doc/libs/release/libs/contract/doc/html/index.html
+
+// IMPORTANT: Do NOT use config macros BOOST_CONTRACT_... in this file so lib
+// .cpp does not need recompiling if config changes (recompile only user code).
+
+#include <boost/contract/core/exception.hpp>
+#include <boost/contract/detail/static_local_var.hpp>
+#include <boost/contract/detail/declspec.hpp>
+#include <boost/thread/lock_guard.hpp>
+#include <boost/thread/mutex.hpp>
+#include <boost/exception/diagnostic_information.hpp>
+#include <boost/config.hpp>
+#include <string>
+#include <sstream>
+#include <iostream>
+#include <exception>
+
+namespace boost { namespace contract {
+
+BOOST_CONTRACT_DETAIL_DECLINLINE
+exception::~exception() BOOST_NOEXCEPT_OR_NOTHROW {}
+
+BOOST_CONTRACT_DETAIL_DECLINLINE
+bad_virtual_result_cast::bad_virtual_result_cast(char const* from_type_name,
+            char const* to_type_name) {
+    std::ostringstream text;
+    text
+        << "incompatible contracted virtual function result type "
+        << "conversion from '" << from_type_name << "' to '"
+        << to_type_name  << "'"
+    ;
+    what_ = text.str();
+}
+
+BOOST_CONTRACT_DETAIL_DECLINLINE
+bad_virtual_result_cast::~bad_virtual_result_cast() BOOST_NOEXCEPT_OR_NOTHROW {}
+
+BOOST_CONTRACT_DETAIL_DECLINLINE
+char const* bad_virtual_result_cast::what() const BOOST_NOEXCEPT_OR_NOTHROW {
+    return what_.c_str();
+}
+
+BOOST_CONTRACT_DETAIL_DECLINLINE
+assertion_failure::assertion_failure(char const* const file,
+        unsigned long const line, char const* const code) :
+    file_(file), line_(line), code_(code)
+{ init(); }
+
+BOOST_CONTRACT_DETAIL_DECLINLINE
+assertion_failure::assertion_failure(char const* const code) :
+    file_(""), line_(0), code_(code)
+{ init(); }
+
+BOOST_CONTRACT_DETAIL_DECLINLINE
+assertion_failure::~assertion_failure() BOOST_NOEXCEPT_OR_NOTHROW {}
+
+BOOST_CONTRACT_DETAIL_DECLINLINE
+char const* assertion_failure::what() const BOOST_NOEXCEPT_OR_NOTHROW {
+    return what_.c_str();
+}
+
+BOOST_CONTRACT_DETAIL_DECLINLINE
+char const* assertion_failure::file() const { return file_; }
+
+BOOST_CONTRACT_DETAIL_DECLINLINE
+unsigned long assertion_failure::line() const { return line_; }
+
+BOOST_CONTRACT_DETAIL_DECLINLINE
+char const* assertion_failure::code() const { return code_; }
+
+BOOST_CONTRACT_DETAIL_DECLINLINE
+void assertion_failure::init() {
+    std::ostringstream text;
+    text << "assertion";
+    if(std::string(code_) != "") text << " \"" << code_ << "\"";
+    text << " failed";
+    if(std::string(file_) != "") {
+        text << ": file \"" << file_ << "\"";
+        if(line_ != 0) text << ", line " << line_;
+    }
+    what_ = text.str();
+}
+
+namespace exception_ {
+    enum failure_key {
+        check_failure_key,
+        pre_failure_key,
+        post_failure_key,
+        except_failure_key,
+        old_failure_key,
+        entry_inv_failure_key,
+        exit_inv_failure_key
+    };
+
+    template<failure_key Key>
+    void default_handler() {
+        std::string k = "";
+        switch(Key) {
+            case check_failure_key: k = "check "; break;
+            case pre_failure_key: k = "precondition "; break;
+            case post_failure_key: k = "postcondition "; break;
+            case except_failure_key: k = "except "; break;
+            case old_failure_key: k = "old copy "; break;
+            case entry_inv_failure_key: k = "entry invariant "; break;
+            case exit_inv_failure_key: k = "exit invariant "; break;
+            // No default (so compiler warning/error on missing enum case).
+        }
+        try { throw; }
+        catch(boost::contract::assertion_failure const& error) {
+            // what = "assertion '...' failed: ...".
+            std::cerr << k << error.what() << std::endl;
+        } catch(...) { // old_failure_key prints this, not above.
+            std::cerr << k << "threw following exception:" << std::endl
+                    << boost::current_exception_diagnostic_information();
+        }
+        std::terminate(); // Default handlers log and call terminate.
+    }
+    
+    template<failure_key Key>
+    void default_from_handler(from) { default_handler<Key>(); }
+
+    // Check failure.
+
+    struct check_failure_mutex_tag;
+    typedef boost::contract::detail::static_local_var<check_failure_mutex_tag,
+            boost::mutex> check_failure_mutex;
+
+    struct check_failure_handler_tag;
+    typedef boost::contract::detail::static_local_var_init<
+        check_failure_handler_tag,
+        failure_handler, 
+        void (*)(),
+        &default_handler<check_failure_key>
+    > check_failure_handler;
+
+    BOOST_CONTRACT_DETAIL_DECLINLINE
+    failure_handler const& set_check_failure_unlocked(failure_handler const& f)
+            BOOST_NOEXCEPT_OR_NOTHROW {
+        check_failure_handler::ref() = f;
+        return f;
+    }
+    
+    BOOST_CONTRACT_DETAIL_DECLINLINE
+    failure_handler const& set_check_failure_locked(failure_handler const& f)
+            BOOST_NOEXCEPT_OR_NOTHROW {
+        boost::lock_guard<boost::mutex> lock(check_failure_mutex::ref());
+        return set_check_failure_unlocked(f);
+    }
+
+    BOOST_CONTRACT_DETAIL_DECLINLINE
+    failure_handler get_check_failure_unlocked() BOOST_NOEXCEPT_OR_NOTHROW {
+        return check_failure_handler::ref();
+    }
+
+    BOOST_CONTRACT_DETAIL_DECLINLINE
+    failure_handler get_check_failure_locked() BOOST_NOEXCEPT_OR_NOTHROW {
+        boost::lock_guard<boost::mutex> lock(check_failure_mutex::ref());
+        return get_check_failure_unlocked();
+    }
+
+    BOOST_CONTRACT_DETAIL_DECLINLINE
+    void check_failure_unlocked() /* can throw */ {
+        check_failure_handler::ref()();
+    }
+    
+    BOOST_CONTRACT_DETAIL_DECLINLINE
+    void check_failure_locked() /* can throw */ {
+        boost::lock_guard<boost::mutex> lock(check_failure_mutex::ref());
+        check_failure_unlocked();
+    }
+    
+    // Precondition failure.
+
+    struct pre_failure_mutex_tag;
+    typedef boost::contract::detail::static_local_var<pre_failure_mutex_tag,
+            boost::mutex> pre_failure_mutex;
+
+    struct pre_failure_handler_tag;
+    typedef boost::contract::detail::static_local_var_init<
+        pre_failure_handler_tag,
+        from_failure_handler,
+        void (*)(from),
+        &default_from_handler<pre_failure_key>
+    > pre_failure_handler;
+
+    BOOST_CONTRACT_DETAIL_DECLINLINE
+    from_failure_handler const& set_pre_failure_unlocked(from_failure_handler
+            const& f) BOOST_NOEXCEPT_OR_NOTHROW {
+        pre_failure_handler::ref() = f;
+        return f;
+    }
+    
+    BOOST_CONTRACT_DETAIL_DECLINLINE
+    from_failure_handler const& set_pre_failure_locked(from_failure_handler
+            const& f) BOOST_NOEXCEPT_OR_NOTHROW {
+        boost::lock_guard<boost::mutex> lock(pre_failure_mutex::ref());
+        return set_pre_failure_unlocked(f);
+    }
+
+    BOOST_CONTRACT_DETAIL_DECLINLINE
+    from_failure_handler get_pre_failure_unlocked() BOOST_NOEXCEPT_OR_NOTHROW {
+        return pre_failure_handler::ref();
+    }
+
+    BOOST_CONTRACT_DETAIL_DECLINLINE
+    from_failure_handler get_pre_failure_locked() BOOST_NOEXCEPT_OR_NOTHROW {
+        boost::lock_guard<boost::mutex> lock(pre_failure_mutex::ref());
+        return get_pre_failure_unlocked();
+    }
+
+    BOOST_CONTRACT_DETAIL_DECLINLINE
+    void pre_failure_unlocked(from where) /* can throw */ {
+        pre_failure_handler::ref()(where);
+    }
+    
+    BOOST_CONTRACT_DETAIL_DECLINLINE
+    void pre_failure_locked(from where) /* can throw */ {
+        boost::lock_guard<boost::mutex> lock(pre_failure_mutex::ref());
+        pre_failure_unlocked(where);
+    }
+    
+    // Postcondition failure.
+
+    struct post_failure_mutex_tag;
+    typedef boost::contract::detail::static_local_var<post_failure_mutex_tag,
+            boost::mutex> post_failure_mutex;
+
+    struct post_failure_handler_tag;
+    typedef boost::contract::detail::static_local_var_init<
+        post_failure_handler_tag,
+        from_failure_handler,
+        void (*)(from),
+        &default_from_handler<post_failure_key>
+    > post_failure_handler;
+
+    BOOST_CONTRACT_DETAIL_DECLINLINE
+    from_failure_handler const& set_post_failure_unlocked(from_failure_handler
+            const& f) BOOST_NOEXCEPT_OR_NOTHROW {
+        post_failure_handler::ref() = f;
+        return f;
+    }
+    
+    BOOST_CONTRACT_DETAIL_DECLINLINE
+    from_failure_handler const& set_post_failure_locked(from_failure_handler
+            const& f) BOOST_NOEXCEPT_OR_NOTHROW {
+        boost::lock_guard<boost::mutex> lock(post_failure_mutex::ref());
+        return set_post_failure_unlocked(f);
+    }
+
+    BOOST_CONTRACT_DETAIL_DECLINLINE
+    from_failure_handler get_post_failure_unlocked() BOOST_NOEXCEPT_OR_NOTHROW {
+        return post_failure_handler::ref();
+    }
+
+    BOOST_CONTRACT_DETAIL_DECLINLINE
+    from_failure_handler get_post_failure_locked() BOOST_NOEXCEPT_OR_NOTHROW {
+        boost::lock_guard<boost::mutex> lock(post_failure_mutex::ref());
+        return get_post_failure_unlocked();
+    }
+
+    BOOST_CONTRACT_DETAIL_DECLINLINE
+    void post_failure_unlocked(from where) /* can throw */ {
+        post_failure_handler::ref()(where);
+    }
+    
+    BOOST_CONTRACT_DETAIL_DECLINLINE
+    void post_failure_locked(from where) /* can throw */ {
+        boost::lock_guard<boost::mutex> lock(post_failure_mutex::ref());
+        post_failure_unlocked(where);
+    }
+    
+    // Except failure.
+
+    struct except_failure_mutex_tag;
+    typedef boost::contract::detail::static_local_var<except_failure_mutex_tag,
+            boost::mutex> except_failure_mutex;
+
+    struct except_failure_handler_tag;
+    typedef boost::contract::detail::static_local_var_init<
+        except_failure_handler_tag,
+        from_failure_handler,
+        void (*)(from),
+        &default_from_handler<except_failure_key>
+    > except_failure_handler;
+
+    BOOST_CONTRACT_DETAIL_DECLINLINE
+    from_failure_handler const& set_except_failure_unlocked(from_failure_handler
+            const& f) BOOST_NOEXCEPT_OR_NOTHROW {
+        except_failure_handler::ref() = f;
+        return f;
+    }
+    
+    BOOST_CONTRACT_DETAIL_DECLINLINE
+    from_failure_handler const& set_except_failure_locked(from_failure_handler
+            const& f) BOOST_NOEXCEPT_OR_NOTHROW {
+        boost::lock_guard<boost::mutex> lock(except_failure_mutex::ref());
+        return set_except_failure_unlocked(f);
+    }
+
+    BOOST_CONTRACT_DETAIL_DECLINLINE
+    from_failure_handler get_except_failure_unlocked()
+            BOOST_NOEXCEPT_OR_NOTHROW {
+        return except_failure_handler::ref();
+    }
+
+    BOOST_CONTRACT_DETAIL_DECLINLINE
+    from_failure_handler get_except_failure_locked() BOOST_NOEXCEPT_OR_NOTHROW {
+        boost::lock_guard<boost::mutex> lock(except_failure_mutex::ref());
+        return get_except_failure_unlocked();
+    }
+
+    BOOST_CONTRACT_DETAIL_DECLINLINE
+    void except_failure_unlocked(from where) /* can throw */ {
+        except_failure_handler::ref()(where);
+    }
+    
+    BOOST_CONTRACT_DETAIL_DECLINLINE
+    void except_failure_locked(from where) /* can throw */ {
+        boost::lock_guard<boost::mutex> lock(except_failure_mutex::ref());
+        except_failure_unlocked(where);
+    }
+
+    // Old-copy failure.
+
+    struct old_failure_mutex_tag;
+    typedef boost::contract::detail::static_local_var<old_failure_mutex_tag,
+            boost::mutex> old_failure_mutex;
+
+    struct old_failure_handler_tag;
+    typedef boost::contract::detail::static_local_var_init<
+        old_failure_handler_tag,
+        from_failure_handler,
+        void (*)(from),
+        &default_from_handler<old_failure_key>
+    > old_failure_handler;
+
+    BOOST_CONTRACT_DETAIL_DECLINLINE
+    from_failure_handler const& set_old_failure_unlocked(from_failure_handler
+            const& f) BOOST_NOEXCEPT_OR_NOTHROW {
+        old_failure_handler::ref() = f;
+        return f;
+    }
+    
+    BOOST_CONTRACT_DETAIL_DECLINLINE
+    from_failure_handler const& set_old_failure_locked(from_failure_handler
+            const& f) BOOST_NOEXCEPT_OR_NOTHROW {
+        boost::lock_guard<boost::mutex> lock(old_failure_mutex::ref());
+        return set_old_failure_unlocked(f);
+    }
+
+    BOOST_CONTRACT_DETAIL_DECLINLINE
+    from_failure_handler get_old_failure_unlocked() BOOST_NOEXCEPT_OR_NOTHROW {
+        return old_failure_handler::ref();
+    }
+
+    BOOST_CONTRACT_DETAIL_DECLINLINE
+    from_failure_handler get_old_failure_locked() BOOST_NOEXCEPT_OR_NOTHROW {
+        boost::lock_guard<boost::mutex> lock(old_failure_mutex::ref());
+        return get_old_failure_unlocked();
+    }
+
+    BOOST_CONTRACT_DETAIL_DECLINLINE
+    void old_failure_unlocked(from where) /* can throw */ {
+        old_failure_handler::ref()(where);
+    }
+    
+    BOOST_CONTRACT_DETAIL_DECLINLINE
+    void old_failure_locked(from where) /* can throw */ {
+        boost::lock_guard<boost::mutex> lock(old_failure_mutex::ref());
+        old_failure_unlocked(where);
+    }
+    
+    // Entry invariant failure.
+
+    struct entry_inv_failure_mutex_tag;
+    typedef boost::contract::detail::static_local_var<
+            entry_inv_failure_mutex_tag, boost::mutex> entry_inv_failure_mutex;
+
+    struct entry_inv_failure_handler_tag;
+    typedef boost::contract::detail::static_local_var_init<
+        entry_inv_failure_handler_tag,
+        from_failure_handler,
+        void (*)(from),
+        &default_from_handler<entry_inv_failure_key>
+    > entry_inv_failure_handler;
+
+    BOOST_CONTRACT_DETAIL_DECLINLINE
+    from_failure_handler const& set_entry_inv_failure_unlocked(
+            from_failure_handler const& f) BOOST_NOEXCEPT_OR_NOTHROW {
+        entry_inv_failure_handler::ref() = f;
+        return f;
+    }
+    
+    BOOST_CONTRACT_DETAIL_DECLINLINE
+    from_failure_handler const& set_entry_inv_failure_locked(
+            from_failure_handler const& f) BOOST_NOEXCEPT_OR_NOTHROW {
+        boost::lock_guard<boost::mutex> lock(entry_inv_failure_mutex::ref());
+        return set_entry_inv_failure_unlocked(f);
+    }
+
+    BOOST_CONTRACT_DETAIL_DECLINLINE
+    from_failure_handler get_entry_inv_failure_unlocked()
+            BOOST_NOEXCEPT_OR_NOTHROW {
+        return entry_inv_failure_handler::ref();
+    }
+
+    BOOST_CONTRACT_DETAIL_DECLINLINE
+    from_failure_handler get_entry_inv_failure_locked()
+            BOOST_NOEXCEPT_OR_NOTHROW {
+        boost::lock_guard<boost::mutex> lock(entry_inv_failure_mutex::ref());
+        return get_entry_inv_failure_unlocked();
+    }
+
+    BOOST_CONTRACT_DETAIL_DECLINLINE
+    void entry_inv_failure_unlocked(from where) /* can throw */ {
+        entry_inv_failure_handler::ref()(where);
+    }
+    
+    BOOST_CONTRACT_DETAIL_DECLINLINE
+    void entry_inv_failure_locked(from where) /* can throw */ {
+        boost::lock_guard<boost::mutex> lock(entry_inv_failure_mutex::ref());
+        entry_inv_failure_unlocked(where);
+    }
+    
+    // Exit invariant failure.
+
+    struct exit_inv_failure_mutex_tag;
+    typedef boost::contract::detail::static_local_var<
+            exit_inv_failure_mutex_tag, boost::mutex> exit_inv_failure_mutex;
+
+    struct exit_inv_failure_handler_tag;
+    typedef boost::contract::detail::static_local_var_init<
+        exit_inv_failure_handler_tag,
+        from_failure_handler,
+        void (*)(from),
+        &default_from_handler<exit_inv_failure_key>
+    > exit_inv_failure_handler;
+
+    BOOST_CONTRACT_DETAIL_DECLINLINE
+    from_failure_handler const& set_exit_inv_failure_unlocked(
+            from_failure_handler const& f) BOOST_NOEXCEPT_OR_NOTHROW {
+        exit_inv_failure_handler::ref() = f;
+        return f;
+    }
+    
+    BOOST_CONTRACT_DETAIL_DECLINLINE
+    from_failure_handler const& set_exit_inv_failure_locked(
+            from_failure_handler const& f) BOOST_NOEXCEPT_OR_NOTHROW {
+        boost::lock_guard<boost::mutex> lock(exit_inv_failure_mutex::ref());
+        return set_exit_inv_failure_unlocked(f);
+    }
+
+    BOOST_CONTRACT_DETAIL_DECLINLINE
+    from_failure_handler get_exit_inv_failure_unlocked()
+            BOOST_NOEXCEPT_OR_NOTHROW {
+        return exit_inv_failure_handler::ref();
+    }
+
+    BOOST_CONTRACT_DETAIL_DECLINLINE
+    from_failure_handler get_exit_inv_failure_locked()
+            BOOST_NOEXCEPT_OR_NOTHROW {
+        boost::lock_guard<boost::mutex> lock(exit_inv_failure_mutex::ref());
+        return get_exit_inv_failure_unlocked();
+    }
+
+    BOOST_CONTRACT_DETAIL_DECLINLINE
+    void exit_inv_failure_unlocked(from where) /* can throw */ {
+        exit_inv_failure_handler::ref()(where);
+    }
+    
+    BOOST_CONTRACT_DETAIL_DECLINLINE
+    void exit_inv_failure_locked(from where) /* can throw */ {
+        boost::lock_guard<boost::mutex> lock(exit_inv_failure_mutex::ref());
+        exit_inv_failure_unlocked(where);
+    }
+}
+
+from_failure_handler const& set_entry_invariant_failure(
+        from_failure_handler const& f) BOOST_NOEXCEPT_OR_NOTHROW;
+
+from_failure_handler const& set_exit_invariant_failure(
+        from_failure_handler const& f) BOOST_NOEXCEPT_OR_NOTHROW;
+
+BOOST_CONTRACT_DETAIL_DECLINLINE
+from_failure_handler const& set_invariant_failure(
+        from_failure_handler const& f)  BOOST_NOEXCEPT_OR_NOTHROW {
+    set_entry_invariant_failure(f);
+    set_exit_invariant_failure(f);
+    return f;
+}
+
+} } // namespace
+
+#endif // #include guard
+

install/boost_1_75_0/include/boost/contract/detail/inlined/detail/checking.hpp

@@ -0,0 +1,49 @@
+
+#ifndef BOOST_CONTRACT_DETAIL_INLINED_DETAIL_CHECKING_HPP_
+#define BOOST_CONTRACT_DETAIL_INLINED_DETAIL_CHECKING_HPP_
+
+// Copyright (C) 2008-2018 Lorenzo Caminiti
+// Distributed under the Boost Software License, Version 1.0 (see accompanying
+// file LICENSE_1_0.txt or a copy at http://www.boost.org/LICENSE_1_0.txt).
+// See: http://www.boost.org/doc/libs/release/libs/contract/doc/html/index.html
+
+// IMPORTANT: Do NOT use config macros BOOST_CONTRACT_... in this file so lib
+// .cpp does not need recompiling if config changes (recompile only user code).
+
+#include <boost/contract/detail/checking.hpp>
+#include <boost/contract/detail/declspec.hpp>
+#include <boost/thread/lock_guard.hpp>
+
+namespace boost { namespace contract { namespace detail {
+
+BOOST_CONTRACT_DETAIL_DECLINLINE
+void checking::init_unlocked() { flag::ref() = true; }
+
+BOOST_CONTRACT_DETAIL_DECLINLINE
+void checking::init_locked() {
+    boost::lock_guard<boost::mutex> lock(mutex::ref());
+    init_unlocked();
+}
+
+BOOST_CONTRACT_DETAIL_DECLINLINE
+void checking::done_unlocked() { flag::ref() = false; }
+
+BOOST_CONTRACT_DETAIL_DECLINLINE
+void checking::done_locked() {
+    boost::lock_guard<boost::mutex> lock(mutex::ref());
+    done_unlocked();
+}
+
+BOOST_CONTRACT_DETAIL_DECLINLINE
+bool checking::already_unlocked() { return flag::ref(); }
+    
+BOOST_CONTRACT_DETAIL_DECLINLINE
+bool checking::already_locked() {
+    boost::lock_guard<boost::mutex> lock(mutex::ref());
+    return already_unlocked();
+}
+
+} } } // namespace
+
+#endif
+

install/boost_1_75_0/include/boost/contract/detail/inlined/old.hpp

@@ -0,0 +1,34 @@
+
+#ifndef BOOST_CONTRACT_DETAIL_INLINED_OLD_HPP_
+#define BOOST_CONTRACT_DETAIL_INLINED_OLD_HPP_
+
+// Copyright (C) 2008-2018 Lorenzo Caminiti
+// Distributed under the Boost Software License, Version 1.0 (see accompanying
+// file LICENSE_1_0.txt or a copy at http://www.boost.org/LICENSE_1_0.txt).
+// See: http://www.boost.org/doc/libs/release/libs/contract/doc/html/index.html
+
+// IMPORTANT: Do NOT use config macros BOOST_CONTRACT_... in this file so lib
+// .cpp does not need recompiling if config changes (recompile only user code).
+
+#include <boost/contract/old.hpp>
+#include <boost/contract/detail/declspec.hpp>
+
+namespace boost { namespace contract {
+
+BOOST_CONTRACT_DETAIL_DECLINLINE
+old_value null_old() { return old_value(); }
+
+BOOST_CONTRACT_DETAIL_DECLINLINE
+old_pointer make_old(old_value const& old) {
+    return old_pointer(0, old);
+}
+
+BOOST_CONTRACT_DETAIL_DECLINLINE
+old_pointer make_old(virtual_* v, old_value const& old) {
+    return old_pointer(v, old);
+}
+
+} } // namespacd
+
+#endif // #include guard
+

install/boost_1_75_0/include/boost/contract/detail/name.hpp

@@ -0,0 +1,26 @@
+
+#ifndef BOOST_CONTRACT_DETAIL_NAME_HPP_
+#define BOOST_CONTRACT_DETAIL_NAME_HPP_
+
+// Copyright (C) 2008-2018 Lorenzo Caminiti
+// Distributed under the Boost Software License, Version 1.0 (see accompanying
+// file LICENSE_1_0.txt or a copy at http://www.boost.org/LICENSE_1_0.txt).
+// See: http://www.boost.org/doc/libs/release/libs/contract/doc/html/index.html
+
+#include <boost/contract/detail/config.hpp>
+#include <boost/preprocessor/cat.hpp>
+
+/* PUBLIC */
+
+// NOTE: Explicitly list number of names to concatenate using ..._NAME-n
+// (instead of using ..._SEQ_CAT or similar) for optimal speed and reentrancy.
+
+#define BOOST_CONTRACT_DETAIL_NAME1(name1) \
+    BOOST_PP_CAT(BOOST_CONTRACT_DETAIL_NAME_PREFIX, name1)
+
+#define BOOST_CONTRACT_DETAIL_NAME2(name1, name2) \
+    BOOST_PP_CAT(BOOST_CONTRACT_DETAIL_NAME_PREFIX, BOOST_PP_CAT(name1, \
+            BOOST_PP_CAT(BOOST_CONTRACT_DETAIL_NAME_INFIX, name2)))
+       
+#endif // #include guard
+

install/boost_1_75_0/include/boost/contract/detail/none.hpp

@@ -0,0 +1,28 @@
+
+#ifndef BOOST_CONTRACT_DETAIL_NONE_HPP_
+#define BOOST_CONTRACT_DETAIL_NONE_HPP_
+
+// Copyright (C) 2008-2018 Lorenzo Caminiti
+// Distributed under the Boost Software License, Version 1.0 (see accompanying
+// file LICENSE_1_0.txt or a copy at http://www.boost.org/LICENSE_1_0.txt).
+// See: http://www.boost.org/doc/libs/release/libs/contract/doc/html/index.html
+
+namespace boost { namespace contract { namespace detail {
+
+// Tag for "no type".
+struct none {
+    // Some lib code use this to avoid unused local var warnings on #if, etc.
+    static none& value() {
+        static none none_value;
+        return none_value;
+    }
+};
+
+// Transform `void` to `none` type (for convenience, instead of using MPL).
+template<typename T> struct none_if_void { typedef T type; };
+template<> struct none_if_void<void> { typedef none type; };
+
+} } } // namespace
+
+#endif // #include guard
+

install/boost_1_75_0/include/boost/contract/detail/noop.hpp

@@ -0,0 +1,19 @@
+
+#ifndef BOOST_CONTRACT_DETAIL_NOOP_HPP_
+#define BOOST_CONTRACT_DETAIL_NOOP_HPP_
+
+// Copyright (C) 2008-2018 Lorenzo Caminiti
+// Distributed under the Boost Software License, Version 1.0 (see accompanying
+// file LICENSE_1_0.txt or a copy at http://www.boost.org/LICENSE_1_0.txt).
+// See: http://www.boost.org/doc/libs/release/libs/contract/doc/html/index.html
+
+// Following must be expressions, not statements (as used with if.., etc.).
+
+#define BOOST_CONTRACT_DETAIL_NOOP ((void)0)
+
+// Following always compiles but never evaluates cond (so check correct syntax).
+#define BOOST_CONTRACT_DETAIL_NOEVAL(cond) \
+    (true || (cond) ? BOOST_CONTRACT_DETAIL_NOOP : BOOST_CONTRACT_DETAIL_NOOP)
+
+#endif // #include guard
+

install/boost_1_75_0/include/boost/contract/detail/operation/constructor.hpp

@@ -0,0 +1,96 @@
+
+#ifndef BOOST_CONTRACT_DETAIL_CONSTRUCTOR_HPP_
+#define BOOST_CONTRACT_DETAIL_CONSTRUCTOR_HPP_
+
+// Copyright (C) 2008-2018 Lorenzo Caminiti
+// Distributed under the Boost Software License, Version 1.0 (see accompanying
+// file LICENSE_1_0.txt or a copy at http://www.boost.org/LICENSE_1_0.txt).
+// See: http://www.boost.org/doc/libs/release/libs/contract/doc/html/index.html
+
+#include <boost/contract/core/exception.hpp>
+#include <boost/contract/core/config.hpp>
+#include <boost/contract/detail/condition/cond_inv.hpp>
+#include <boost/contract/detail/none.hpp>
+#include <boost/contract/detail/exception.hpp>
+#if     !defined(BOOST_CONTRACT_ALL_DISABLE_NO_ASSERTION) && ( \
+        !defined(BOOST_CONTRACT_NO_INVARIANTS) || \
+        !defined(BOOST_CONTRACT_NO_POSTCONDITIONS) || \
+        !defined(BOOST_CONTRACT_NO_EXCEPTS))
+    #include <boost/contract/detail/checking.hpp>
+#endif
+#if     !defined(BOOST_CONTRACT_NO_EXIT_INVARIANTS) || \
+        !defined(BOOST_CONTRACT_NO_POSTCONDITIONS) || \
+        !defined(BOOST_CONTRACT_NO_EXCEPTS)
+    #include <boost/config.hpp>
+    #include <exception>
+#endif
+
+namespace boost { namespace contract { namespace detail {
+
+// Ctor subcontracting impl via C++ obj construction mechanism.
+template<class C> // Non-copyable base.
+class constructor : public cond_inv</* VR = */ none, C> {
+public:
+    explicit constructor(C* obj) : cond_inv</* VR = */ none, C>(
+            boost::contract::from_constructor, obj) {}
+
+private:
+    #if     !defined(BOOST_CONTRACT_NO_ENTRY_INVARIANTS) || \
+            !defined(BOOST_CONTRACT_NO_OLDS)
+        void init() /* override */ {
+            #ifndef BOOST_CONTRACT_ALL_DISABLE_NO_ASSERTION
+                if(checking::already()) return;
+            #endif
+
+            #ifndef BOOST_CONTRACT_NO_ENTRY_INVARIANTS
+                {
+                    #ifndef BOOST_CONTRACT_ALL_DISABLE_NO_ASSERTION
+                        checking k;
+                    #endif
+                    this->check_entry_static_inv();
+                    // No object before ctor body so check only static inv at
+                    // entry. Ctor pre checked by constructor_precondition.
+                }
+            #endif
+            #ifndef BOOST_CONTRACT_NO_OLDS
+                this->copy_old();
+            #endif
+        }
+    #endif
+
+public:
+    #if     !defined(BOOST_CONTRACT_NO_EXIT_INVARIANTS) || \
+            !defined(BOOST_CONTRACT_NO_POSTCONDITIONS) || \
+            !defined(BOOST_CONTRACT_NO_EXCEPTS)
+        ~constructor() BOOST_NOEXCEPT_IF(false) {
+            this->assert_initialized();
+            #ifndef BOOST_CONTRACT_ALL_DISABLE_NO_ASSERTION
+                if(checking::already()) return;
+                checking k;
+            #endif
+
+            // If ctor body threw, no obj so check only static inv. Otherwise,
+            // obj constructed so check static inv, non-static inv, and post.
+            if(uncaught_exception()) {
+                #ifndef BOOST_CONTRACT_NO_EXIT_INVARIANTS
+                    this->check_exit_static_inv();
+                #endif
+                #ifndef BOOST_CONTRACT_NO_EXCEPTS
+                    this->check_except();
+                #endif
+            } else {
+                #ifndef BOOST_CONTRACT_NO_EXIT_INVARIANTS
+                    this->check_exit_all_inv();
+                #endif
+                #ifndef BOOST_CONTRACT_NO_POSTCONDITIONS
+                    this->check_post(none());
+                #endif
+            }
+        }
+    #endif
+};
+
+} } } // namespace
+
+#endif // #include guard
+

install/boost_1_75_0/include/boost/contract/detail/operation/destructor.hpp

@@ -0,0 +1,103 @@
+
+#ifndef BOOST_CONTRACT_DETAIL_DESTRUCTOR_HPP_
+#define BOOST_CONTRACT_DETAIL_DESTRUCTOR_HPP_
+
+// Copyright (C) 2008-2018 Lorenzo Caminiti
+// Distributed under the Boost Software License, Version 1.0 (see accompanying
+// file LICENSE_1_0.txt or a copy at http://www.boost.org/LICENSE_1_0.txt).
+// See: http://www.boost.org/doc/libs/release/libs/contract/doc/html/index.html
+
+#include <boost/contract/core/exception.hpp>
+#include <boost/contract/core/config.hpp>
+#include <boost/contract/detail/condition/cond_inv.hpp>
+#include <boost/contract/detail/none.hpp>
+#include <boost/contract/detail/exception.hpp>
+#if     !defined(BOOST_CONTRACT_ALL_DISABLE_NO_ASSERTION) && ( \
+        !defined(BOOST_CONTRACT_NO_INVARIANTS) || \
+        !defined(BOOST_CONTRACT_NO_POSTCONDITIONS) || \
+        !defined(BOOST_CONTRACT_NO_EXCEPTS))
+    #include <boost/contract/detail/checking.hpp>
+#endif
+#if     !defined(BOOST_CONTRACT_NO_EXIT_INVARIANTS) || \
+        !defined(BOOST_CONTRACT_NO_POSTCONDITIONS) || \
+        !defined(BOOST_CONTRACT_NO_EXCEPTS)
+    #include <boost/config.hpp>
+    #include <exception>
+#endif
+
+namespace boost { namespace contract { namespace detail {
+
+// Dtor subcontracting impl via C++ obj destruction mechanism.
+template<class C> // Non-copyable base.
+class destructor : public cond_inv</* VR = */ none, C> {
+public:
+    explicit destructor(C* obj) : cond_inv</* VR = */ none, C>(
+            boost::contract::from_destructor, obj) {}
+
+private:
+    #if     !defined(BOOST_CONTRACT_NO_ENTRY_INVARIANTS) || \
+            !defined(BOOST_CONTRACT_NO_OLDS)
+        void init() /* override */ {
+            #ifndef BOOST_CONTRACT_ALL_DISABLE_NO_ASSERTION
+                if(checking::already()) return;
+            #endif
+
+            #ifndef BOOST_CONTRACT_NO_ENTRY_INVARIANTS
+                {
+                    #ifndef BOOST_CONTRACT_ALL_DISABLE_NO_ASSERTION
+                        checking k;
+                    #endif
+                    // Obj exists (before dtor body), check static and non- inv.
+                    this->check_entry_all_inv();
+                    // Dtor cannot have pre because it has no parameters.
+                }
+            #endif
+            #ifndef BOOST_CONTRACT_NO_OLDS
+                this->copy_old();
+            #endif
+        }
+    #endif
+    
+public:
+    #if     !defined(BOOST_CONTRACT_NO_EXIT_INVARIANTS) || \
+            !defined(BOOST_CONTRACT_NO_POSTCONDITIONS) || \
+            !defined(BOOST_CONTRACT_NO_EXCEPTS)
+        ~destructor() BOOST_NOEXCEPT_IF(false) {
+            this->assert_initialized();
+            #ifndef BOOST_CONTRACT_ALL_DISABLE_NO_ASSERTION
+                if(checking::already()) return;
+                checking k;
+            #endif
+
+            // If dtor body threw, obj still exists so check subcontracted
+            // static and non- inv (but no post because of throw). Otherwise,
+            // obj destructed so check static inv and post (even if there is no
+            // obj after dtor body, this library allows dtor post, for example
+            // to check static members for an instance counter class).
+            // NOTE: In theory C++ destructors should not throw, but the
+            // language allows for that (even if in C++11 dtors declarations are
+            // implicitly noexcept(true) unless specified otherwise) so this
+            // library must handle such a case.
+            if(uncaught_exception()) {
+                #ifndef BOOST_CONTRACT_NO_EXIT_INVARIANTS
+                    this->check_exit_all_inv();
+                #endif
+                #ifndef BOOST_CONTRACT_NO_EXCEPTS
+                    this->check_except();
+                #endif
+            } else {
+                #ifndef BOOST_CONTRACT_NO_EXIT_INVARIANTS
+                    this->check_exit_static_inv();
+                #endif
+                #ifndef BOOST_CONTRACT_NO_POSTCONDITIONS
+                    this->check_post(none());
+                #endif
+            }
+        }
+    #endif
+};
+
+} } } // namespace
+
+#endif // #include guard
+

install/boost_1_75_0/include/boost/contract/detail/operation/function.hpp

@@ -0,0 +1,83 @@
+
+#ifndef BOOST_CONTRACT_DETAIL_FUNCTION_HPP_
+#define BOOST_CONTRACT_DETAIL_FUNCTION_HPP_
+
+// Copyright (C) 2008-2018 Lorenzo Caminiti
+// Distributed under the Boost Software License, Version 1.0 (see accompanying
+// file LICENSE_1_0.txt or a copy at http://www.boost.org/LICENSE_1_0.txt).
+// See: http://www.boost.org/doc/libs/release/libs/contract/doc/html/index.html
+
+#include <boost/contract/core/exception.hpp>
+#include <boost/contract/core/config.hpp>
+#include <boost/contract/detail/condition/cond_post.hpp>
+#include <boost/contract/detail/exception.hpp>
+#if     !defined(BOOST_CONTRACT_ALL_DISABLE_NO_ASSERTION) && ( \
+        !defined(BOOST_CONTRACT_NO_PRECONDITIONS) || \
+        !defined(BOOST_CONTRACT_NO_POSTCONDITIONS) || \
+        !defined(BOOST_CONTRACT_NO_EXCEPTS))
+    #include <boost/contract/detail/checking.hpp>
+#endif
+#if     !defined(BOOST_CONTRACT_NO_POSTCONDITIONS) || \
+        !defined(BOOST_CONTRACT_NO_EXCEPTS)
+    #include <boost/config.hpp>
+    #include <exception>
+#endif
+
+namespace boost { namespace contract { namespace detail {
+
+// Used for free function, private and protected member functions.
+class function : public cond_post</* VR = */ none> { // Non-copyable base.
+public:
+    explicit function() : cond_post</* VR = */ none>(
+            boost::contract::from_function) {}
+
+private:
+    #if     !defined(BOOST_CONTRACT_NO_PRECONDITIONS) || \
+            !defined(BOOST_CONTRACT_NO_OLDS)
+        void init() /* override */ {
+            #ifndef  BOOST_CONTRACT_ALL_DISABLE_NO_ASSERTION
+                if(checking::already()) return;
+            #endif
+            #ifndef BOOST_CONTRACT_NO_PRECONDITIONS
+                {
+                    #if !defined(BOOST_CONTRACT_ALL_DISABLE_NO_ASSERTION) && \
+                        !defined( \
+                            BOOST_CONTRACT_PRECONDITIONS_DISABLE_NO_ASSERTION)
+                        checking k;
+                    #endif
+                    this->check_pre();
+                }
+            #endif
+            #ifndef BOOST_CONTRACT_NO_OLDS
+                this->copy_old();
+            #endif
+        }
+    #endif
+
+public:
+    #if     !defined(BOOST_CONTRACT_NO_POSTCONDITIONS) || \
+            !defined(BOOST_CONTRACT_NO_EXCEPTS)
+        ~function() BOOST_NOEXCEPT_IF(false) {
+            this->assert_initialized();
+            #ifndef  BOOST_CONTRACT_ALL_DISABLE_NO_ASSERTION
+                if(checking::already()) return;
+                checking k;
+            #endif
+            
+            if(uncaught_exception()) {
+                #ifndef BOOST_CONTRACT_NO_EXCEPTS
+                    this->check_except();
+                #endif
+            } else {
+                #ifndef BOOST_CONTRACT_NO_POSTCONDITIONS
+                    this->check_post(none());
+                #endif
+            }
+        }
+    #endif
+};
+
+} } } // namespace
+
+#endif // #include guard
+

install/boost_1_75_0/include/boost/contract/detail/operation/public_function.hpp

@@ -0,0 +1,162 @@
+
+#ifndef BOOST_CONTRACT_DETAIL_PUBLIC_FUNCTION_HPP_
+#define BOOST_CONTRACT_DETAIL_PUBLIC_FUNCTION_HPP_
+
+// Copyright (C) 2008-2018 Lorenzo Caminiti
+// Distributed under the Boost Software License, Version 1.0 (see accompanying
+// file LICENSE_1_0.txt or a copy at http://www.boost.org/LICENSE_1_0.txt).
+// See: http://www.boost.org/doc/libs/release/libs/contract/doc/html/index.html
+
+#include <boost/contract/core/virtual.hpp>
+#include <boost/contract/core/exception.hpp>
+#include <boost/contract/core/config.hpp>
+#include <boost/contract/core/virtual.hpp>
+#include <boost/contract/detail/condition/cond_subcontracting.hpp>
+#include <boost/contract/detail/tvariadic.hpp>
+#include <boost/contract/detail/exception.hpp>
+#if     !defined(BOOST_CONTRACT_ALL_DISABLE_NO_ASSERTION) && ( \
+        !defined(BOOST_CONTRACT_NO_INVARIANTS) || \
+        !defined(BOOST_CONTRACT_NO_PRECONDITIONS) || \
+        !defined(BOOST_CONTRACT_NO_POSTCONDITIONS) || \
+        !defined(BOOST_CONTRACT_NO_EXCEPTS))
+    #include <boost/contract/detail/checking.hpp>
+#endif
+#if     !defined(BOOST_CONTRACT_NO_EXIT_INVARIANTS) || \
+        !defined(BOOST_CONTRACT_NO_POSTCONDITIONS) || \
+        !defined(BOOST_CONTRACT_NO_EXCEPTS)
+    #include <boost/config.hpp>
+#endif
+#if     !defined(BOOST_CONTRACT_NO_POSTCONDITIONS) || \
+        !defined(BOOST_CONTRACT_NO_EXCEPTS)
+    #include <exception>
+#endif
+
+namespace boost { namespace contract { namespace detail {
+
+template<
+    class O, typename VR, typename F, class C
+    BOOST_CONTRACT_DETAIL_TVARIADIC_COMMA(BOOST_CONTRACT_MAX_ARGS)
+    BOOST_CONTRACT_DETAIL_TVARIADIC_TPARAMS_Z(1, BOOST_CONTRACT_MAX_ARGS, Args)
+>
+class public_function : // Non-copyable base.
+    public cond_subcontracting<
+        O, VR, F, C
+        BOOST_CONTRACT_DETAIL_TVARIADIC_COMMA(BOOST_CONTRACT_MAX_ARGS)
+        BOOST_CONTRACT_DETAIL_TVARIADIC_ARGS_Z(1, BOOST_CONTRACT_MAX_ARGS, Args)
+    >
+{
+public:
+    explicit public_function(
+        boost::contract::virtual_* v, C* obj, VR& r
+        BOOST_CONTRACT_DETAIL_TVARIADIC_COMMA(BOOST_CONTRACT_MAX_ARGS)
+        BOOST_CONTRACT_DETAIL_TVARIADIC_FPARAMS_Z(1,
+                BOOST_CONTRACT_MAX_ARGS, Args, &, args)
+    ) :
+        cond_subcontracting<
+            O, VR, F, C
+            BOOST_CONTRACT_DETAIL_TVARIADIC_COMMA(BOOST_CONTRACT_MAX_ARGS)
+            BOOST_CONTRACT_DETAIL_TVARIADIC_ARGS_Z(1,
+                    BOOST_CONTRACT_MAX_ARGS, Args)
+        >(
+            boost::contract::from_function, v, obj, r
+            BOOST_CONTRACT_DETAIL_TVARIADIC_COMMA(BOOST_CONTRACT_MAX_ARGS)
+            BOOST_CONTRACT_DETAIL_TVARIADIC_ARGS_Z(1,
+                    BOOST_CONTRACT_MAX_ARGS, args)
+        )
+    {}
+
+private:
+    #if     !defined(BOOST_CONTRACT_NO_INVARIANTS) || \
+            !defined(BOOST_CONTRACT_NO_PRECONDITIONS) || \
+            !defined(BOOST_CONTRACT_NO_POSTCONDITIONS) || \
+            !defined(BOOST_CONTRACT_NO_EXCEPTS)
+        void init() /* override */ {
+            #if     !defined(BOOST_CONTRACT_NO_POSTCONDITIONS) || \
+                    !defined(BOOST_CONTRACT_NO_EXCEPTS)
+                this->init_subcontracted_old();
+            #endif
+            if(!this->base_call()) {
+                #ifndef BOOST_CONTRACT_ALL_DISABLE_NO_ASSERTION
+                    if(checking::already()) return;
+                #endif
+                { // Acquire checking guard.
+                    #ifndef BOOST_CONTRACT_ALL_DISABLE_NO_ASSERTION
+                        checking k;
+                    #endif
+                    #ifndef BOOST_CONTRACT_NO_ENTRY_INVARIANTS
+                        this->check_subcontracted_entry_inv();
+                    #endif
+                    #ifndef BOOST_CONTRACT_NO_PRECONDITIONS
+                        #ifndef \
+  BOOST_CONTRACT_PRECONDITIONS_DISABLE_NO_ASSERTION
+                            this->check_subcontracted_pre();
+                            } // Release checking guard (after pre check).
+                        #else
+                            } // Release checking guard (before pre check).
+                            this->check_subcontracted_pre();
+                        #endif
+                    #else
+                        } // Release checking guard.
+                    #endif
+                #ifndef BOOST_CONTRACT_NO_OLDS
+                    this->copy_subcontracted_old();
+                #endif
+            } else {
+                #ifndef BOOST_CONTRACT_NO_ENTRY_INVARIANTS
+                    this->check_subcontracted_entry_inv();
+                #endif
+                #ifndef BOOST_CONTRACT_NO_PRECONDITIONS
+                    this->check_subcontracted_pre();
+                #endif
+                #ifndef BOOST_CONTRACT_NO_OLDS
+                    this->copy_subcontracted_old();
+                #endif
+                #ifndef BOOST_CONTRACT_NO_EXIT_INVARIANTS
+                    this->check_subcontracted_exit_inv();
+                #endif
+                if(uncaught_exception()) {
+                    #ifndef BOOST_CONTRACT_NO_EXCEPTS
+                        this->check_subcontracted_except();
+                    #endif
+                } else {
+                    #ifndef BOOST_CONTRACT_NO_POSTCONDITIONS
+                        this->check_subcontracted_post();
+                    #endif
+                }
+            }
+        }
+    #endif
+
+public:
+    #if     !defined(BOOST_CONTRACT_NO_EXIT_INVARIANTS) || \
+            !defined(BOOST_CONTRACT_NO_POSTCONDITIONS) || \
+            !defined(BOOST_CONTRACT_NO_EXCEPTS)
+        ~public_function() BOOST_NOEXCEPT_IF(false) {
+            this->assert_initialized();
+            if(!this->base_call()) {
+                #ifndef BOOST_CONTRACT_ALL_DISABLE_NO_ASSERTION
+                    if(checking::already()) return;
+                    checking k;
+                #endif
+
+                #ifndef BOOST_CONTRACT_NO_EXIT_INVARIANTS
+                    this->check_subcontracted_exit_inv();
+                #endif
+                if(uncaught_exception()) {
+                    #ifndef BOOST_CONTRACT_NO_EXCEPTS
+                        this->check_subcontracted_except();
+                    #endif
+                } else {
+                    #ifndef BOOST_CONTRACT_NO_POSTCONDITIONS
+                        this->check_subcontracted_post();
+                    #endif
+                }
+            }
+        }
+    #endif
+};
+
+} } } // namespace
+
+#endif // #include guard
+

install/boost_1_75_0/include/boost/contract/detail/operation/static_public_function.hpp

@@ -0,0 +1,104 @@
+
+#ifndef BOOST_CONTRACT_DETAIL_STATIC_PUBLIC_FUNCTION_HPP_
+#define BOOST_CONTRACT_DETAIL_STATIC_PUBLIC_FUNCTION_HPP_
+
+// Copyright (C) 2008-2018 Lorenzo Caminiti
+// Distributed under the Boost Software License, Version 1.0 (see accompanying
+// file LICENSE_1_0.txt or a copy at http://www.boost.org/LICENSE_1_0.txt).
+// See: http://www.boost.org/doc/libs/release/libs/contract/doc/html/index.html
+
+#include <boost/contract/core/exception.hpp>
+#include <boost/contract/core/config.hpp>
+#include <boost/contract/detail/condition/cond_inv.hpp>
+#include <boost/contract/detail/none.hpp>
+#include <boost/contract/detail/exception.hpp>
+#if     !defined(BOOST_CONTRACT_ALL_DISABLE_NO_ASSERTION) && ( \
+        !defined(BOOST_CONTRACT_NO_INVARIANTS) || \
+        !defined(BOOST_CONTRACT_NO_PRECONDITIONS) || \
+        !defined(BOOST_CONTRACT_NO_POSTCONDITIONS) || \
+        !defined(BOOST_CONTRACT_NO_EXCEPTS))
+    #include <boost/contract/detail/checking.hpp>
+#endif
+#if     !defined(BOOST_CONTRACT_NO_EXIT_INVARIANTS) || \
+        !defined(BOOST_CONTRACT_NO_POSTCONDITIONS) || \
+        !defined(BOOST_CONTRACT_NO_EXCEPTS)
+    #include <boost/config.hpp>
+    #include <exception>
+#endif
+
+namespace boost { namespace contract { namespace detail {
+
+// No subcontracting because static so no obj and no substitution principle.
+template<class C> // Non-copyable base.
+class static_public_function : public cond_inv</* VR = */ none, C> {
+public:
+    explicit static_public_function() : cond_inv</* VR = */ none, C>(
+            boost::contract::from_function, /* obj = */ 0) {}
+
+private:
+    #if     !defined(BOOST_CONTRACT_NO_ENTRY_INVARIANTS) || \
+            !defined(BOOST_CONTRACT_NO_PRECONDITIONS) || \
+            !defined(BOOST_CONTRACT_NO_OLDS)
+        void init() /* override */ {
+            #ifndef BOOST_CONTRACT_ALL_DISABLE_NO_ASSERTION
+                if(checking::already()) return;
+            #endif
+            #if !defined(BOOST_CONTRACT_NO_ENTRY_INVARIANTS) || \
+                    !defined(BOOST_CONTRACT_NO_PRECONDITIONS)
+                { // Acquire checking guard.
+                    #ifndef BOOST_CONTRACT_ALL_DISABLE_NO_ASSERTION
+                        checking k;
+                    #endif
+                    #ifndef BOOST_CONTRACT_NO_ENTRY_INVARIANTS
+                        this->check_entry_static_inv();
+                    #endif
+                    #ifndef BOOST_CONTRACT_NO_PRECONDITIONS
+                        #ifndef \
+  BOOST_CONTRACT_PRECONDITIONS_DISABLE_NO_ASSERTION
+                            this->check_pre();
+                            } // Release checking guard (after pre check).
+                        #else
+                            } // Release checking guard (before pre check).
+                            this->check_pre();
+                        #endif
+                    #else
+                        } // Release checking guard
+                    #endif
+            #endif
+            #ifndef BOOST_CONTRACT_NO_OLDS
+                this->copy_old();
+            #endif
+        }
+    #endif
+
+public:
+    #if     !defined(BOOST_CONTRACT_NO_EXIT_INVARIANTS) || \
+            !defined(BOOST_CONTRACT_NO_POSTCONDITIONS) || \
+            !defined(BOOST_CONTRACT_NO_EXCEPTS)
+        ~static_public_function() BOOST_NOEXCEPT_IF(false) {
+            this->assert_initialized();
+            #ifndef BOOST_CONTRACT_ALL_DISABLE_NO_ASSERTION
+                if(checking::already()) return;
+                checking k;
+            #endif
+
+            #ifndef BOOST_CONTRACT_NO_EXIT_INVARIANTS
+                this->check_exit_static_inv();
+            #endif
+            if(uncaught_exception()) {
+                #ifndef BOOST_CONTRACT_NO_EXCEPTS
+                    this->check_except();
+                #endif
+            } else {
+                #ifndef BOOST_CONTRACT_NO_POSTCONDITIONS
+                    this->check_post(none());
+                #endif
+            }
+        }
+    #endif
+};
+
+} } } // namespace
+
+#endif // #include guard
+

install/boost_1_75_0/include/boost/contract/detail/operator_safe_bool.hpp

@@ -0,0 +1,73 @@
+
+#ifndef BOOST_CONTRACT_DETAIL_OPERATOR_SAFE_BOOL_HPP_
+#define BOOST_CONTRACT_DETAIL_OPERATOR_SAFE_BOOL_HPP_
+
+// Copyright (C) 2008-2018 Lorenzo Caminiti
+// Distributed under the Boost Software License, Version 1.0 (see accompanying
+// file LICENSE_1_0.txt or a copy at http://www.boost.org/LICENSE_1_0.txt).
+// See: http://www.boost.org/doc/libs/release/libs/contract/doc/html/index.html
+
+#include <boost/contract/detail/name.hpp>
+#include <boost/config.hpp>
+#include <boost/detail/workaround.hpp>
+
+// NOTE: This code is inspired by <boost/shared_ptr/detail/operator_bool.hpp>.
+
+/* PRIVATE */
+
+// operator! is redundant, but some compilers need it.
+#define BOOST_CONTRACT_OPERATOR_SAFE_BOOL_NOT_(bool_expr) \
+    bool operator!() const BOOST_NOEXCEPT { return !(bool_expr); }
+    
+/* PUBLIC */
+
+#if !defined(BOOST_NO_CXX11_EXPLICIT_CONVERSION_OPERATORS) && \
+        !defined(BOOST_NO_CXX11_NULLPTR)
+    #define BOOST_CONTRACT_DETAIL_OPERATOR_SAFE_BOOL(this_type, bool_expr) \
+        explicit operator bool() const BOOST_NOEXCEPT { return (bool_expr); } \
+        BOOST_CONTRACT_OPERATOR_SAFE_BOOL_NOT_(bool_expr)
+#elif (defined(__SUNPRO_CC) && BOOST_WORKAROUND(__SUNPRO_CC, < 0x570) ) || \
+        defined(__CINT__)
+    #define BOOST_CONTRACT_DETAIL_OPERATOR_SAFE_BOOL(this_type, bool_expr) \
+        operator bool() const BOOST_NOEXCEPT { return (bool_expr); } \
+        BOOST_CONTRACT_OPERATOR_SAFE_BOOL_NOT_(bool_expr)
+#elif defined(_MANAGED)
+    #define BOOST_CONTRACT_DETAIL_OPERATOR_SAFE_BOOL(this_type, bool_expr) \
+        static void BOOST_CONTRACT_DETAIL_NAME1(operator_safe_bool_func)( \
+                this_type***) {} \
+        typedef void (*BOOST_CONTRACT_DETAIL_NAME1(operator_safe_bool_type))( \
+                this_type***); \
+        operator BOOST_CONTRACT_DETAIL_NANE(operator_safe_bool_type)() \
+                const BOOST_NOEXCEPT { \
+            return (bool_expr) ? \
+                    &BOOST_CONTRACT_DETAIL_NAME1(operator_safe_bool_func) : 0; \
+        } \
+        BOOST_CONTRACT_OPERATOR_SAFE_BOOL_NOT_(bool_expr)
+#elif (defined(__MWERKS__) && BOOST_WORKAROUND(__MWERKS__, < 0x3200)) || \
+        (defined(__GNUC__) && (__GNUC__ * 100 + __GNUC_MINOR__ < 304)) || \
+        (defined(__SUNPRO_CC) && BOOST_WORKAROUND(__SUNPRO_CC, <= 0x590))
+    #define BOOST_CONTRACT_DETAIL_OPERATOR_SAFE_BOOL(this_type, bool_expr) \
+        void BOOST_CONTRACT_DETAIL_NAME1(operator_safe_bool_func)() const {} \
+        typedef void (this_type::*BOOST_CONTRACT_DETAIL_NAME1( \
+                operator_safe_bool_type))() const; \
+        operator BOOST_CONTRACT_DETAIL_NAME1(operator_safe_bool_type)() \
+                const BOOST_NOEXCEPT { \
+            return (bool_expr) ? &this_type:: \
+                    BOOST_CONTRACT_DETAIL_NAME1(operator_safe_bool_func) : 0; \
+        } \
+        BOOST_CONTRACT_OPERATOR_SAFE_BOOL_NOT_(bool_expr)
+#else
+    #define BOOST_CONTRACT_DETAIL_OPERATOR_SAFE_BOOL(this_type, bool_expr) \
+        void* BOOST_CONTRACT_DETAIL_NAME1(operator_safe_bool_data); \
+        typedef void* this_type::*BOOST_CONTRACT_DETAIL_NAME1( \
+                operator_safe_bool_type);\
+        operator BOOST_CONTRACT_DETAIL_NAME1(operator_safe_bool_type)() \
+                const BOOST_NOEXCEPT { \
+            return (bool_expr) ? &this_type:: \
+                    BOOST_CONTRACT_DETAIL_NAME1(operator_safe_bool_data) : 0; \
+        } \
+        BOOST_CONTRACT_OPERATOR_SAFE_BOOL_NOT_(bool_expr)
+#endif
+
+#endif // #include guard
+

install/boost_1_75_0/include/boost/contract/detail/preprocessor/keyword/private.hpp

@@ -0,0 +1,35 @@
+
+#ifndef BOOST_CONTRACT_DETAIL_PP_KEYWORD_PRIVATE_HPP_
+#define BOOST_CONTRACT_DETAIL_PP_KEYWORD_PRIVATE_HPP_
+
+// Copyright (C) 2008-2018 Lorenzo Caminiti
+// Distributed under the Boost Software License, Version 1.0 (see accompanying
+// file LICENSE_1_0.txt or a copy at http://www.boost.org/LICENSE_1_0.txt).
+// See: http://www.boost.org/doc/libs/release/libs/contract/doc/html/index.html
+
+#include <boost/contract/detail/preprocessor/keyword/utility/is.hpp>
+#include <boost/preprocessor/cat.hpp>
+
+/* PRIVATE */
+
+// Must expand to a single comma `,` (not local macros, do not #undefine).
+#define BOOST_CONTRACT_DETAIL_PP_KEYWORD_PRIVATE_CAT_TO_COMMAprivate ,
+
+// Must expand to empty `` (not local macros, do not #undefine).
+#define BOOST_CONTRACT_DETAIL_PP_KEYWORD_PRIVATE_CAT_TO_EMPTYprivate
+
+/* PUBLIC */
+
+// Precondition: tokens must start with a token concatenable to a macro name
+//               (e.g., a literal or integral token).
+#define BOOST_CONTRACT_DETAIL_PP_KEYWORD_IS_PRIVATE(tokens) \
+    BOOST_CONTRACT_DETAIL_PP_KEYWORD_UTILITY_IS( \
+            BOOST_CONTRACT_DETAIL_PP_KEYWORD_PRIVATE_CAT_TO_COMMA, tokens)
+
+// Precondition: tokens must start with `private` (this can be
+//               checked with `..._IS_PRIVATE` macro above).
+#define BOOST_CONTRACT_DETAIL_PP_KEYWORD_REMOVE_PRIVATE(tokens) \
+    BOOST_PP_CAT(BOOST_CONTRACT_DETAIL_PP_KEYWORD_PRIVATE_CAT_TO_EMPTY, tokens)
+
+#endif // #include guard
+

install/boost_1_75_0/include/boost/contract/detail/preprocessor/keyword/protected.hpp

@@ -0,0 +1,36 @@
+
+#ifndef BOOST_CONTRACT_DETAIL_PP_KEYWORD_PROTECTED_HPP_
+#define BOOST_CONTRACT_DETAIL_PP_KEYWORD_PROTECTED_HPP_
+
+// Copyright (C) 2008-2018 Lorenzo Caminiti
+// Distributed under the Boost Software License, Version 1.0 (see accompanying
+// file LICENSE_1_0.txt or a copy at http://www.boost.org/LICENSE_1_0.txt).
+// See: http://www.boost.org/doc/libs/release/libs/contract/doc/html/index.html
+
+#include <boost/contract/detail/preprocessor/keyword/utility/is.hpp>
+#include <boost/preprocessor/cat.hpp>
+
+/* PRIVATE */
+
+// Must expand to a single comma `,` (not local macros, do not #undefine).
+#define BOOST_CONTRACT_DETAIL_PP_KEYWORD_PROTECTED_CAT_TO_COMMAprotected ,
+
+// Must expand to empty `` (not local macros, do not #undefine).
+#define BOOST_CONTRACT_DETAIL_PP_KEYWORD_PROTECTED_CAT_TO_EMPTYprotected
+
+/* PUBLIC */
+
+// Precondition: tokens must start with a token concatenable to a macro name
+//               (e.g., a literal or integral token).
+#define BOOST_CONTRACT_DETAIL_PP_KEYWORD_IS_PROTECTED(tokens) \
+    BOOST_CONTRACT_DETAIL_PP_KEYWORD_UTILITY_IS( \
+            BOOST_CONTRACT_DETAIL_PP_KEYWORD_PROTECTED_CAT_TO_COMMA, tokens)
+
+// Precondition: tokens must start with `protected` (this can be
+//               checked with `..._IS_PROTECTED` macro above).
+#define BOOST_CONTRACT_DETAIL_PP_KEYWORD_REMOVE_PROTECTED(tokens) \
+    BOOST_PP_CAT(BOOST_CONTRACT_DETAIL_PP_KEYWORD_PROTECTED_CAT_TO_EMPTY, \
+            tokens)
+
+#endif // #include guard
+

install/boost_1_75_0/include/boost/contract/detail/preprocessor/keyword/public.hpp

@@ -0,0 +1,35 @@
+
+#ifndef BOOST_CONTRACT_DETAIL_PP_KEYWORD_PUBLIC_HPP_
+#define BOOST_CONTRACT_DETAIL_PP_KEYWORD_PUBLIC_HPP_
+
+// Copyright (C) 2008-2018 Lorenzo Caminiti
+// Distributed under the Boost Software License, Version 1.0 (see accompanying
+// file LICENSE_1_0.txt or a copy at http://www.boost.org/LICENSE_1_0.txt).
+// See: http://www.boost.org/doc/libs/release/libs/contract/doc/html/index.html
+
+#include <boost/contract/detail/preprocessor/keyword/utility/is.hpp>
+#include <boost/preprocessor/cat.hpp>
+
+/* PRIVATE */
+
+// Must expand to a single comma `,` (not local macros, do not #undefine).
+#define BOOST_CONTRACT_DETAIL_PP_KEYWORD_PUBLIC_CAT_TO_COMMApublic ,
+
+// Must expand to empty `` (not local macros, do not #undefine).
+#define BOOST_CONTRACT_DETAIL_PP_KEYWORD_PUBLIC_CAT_TO_EMPTYpublic
+
+/* PUBLIC */
+
+// Precondition: tokens must start with a token concatenable to a macro name
+//               (e.g., a literal or integral token).
+#define BOOST_CONTRACT_DETAIL_PP_KEYWORD_IS_PUBLIC(tokens) \
+    BOOST_CONTRACT_DETAIL_PP_KEYWORD_UTILITY_IS( \
+            BOOST_CONTRACT_DETAIL_PP_KEYWORD_PUBLIC_CAT_TO_COMMA, tokens)
+
+// Precondition: tokens must start with `public` (this can be
+//               checked with `..._IS_PUBLIC` macro above).
+#define BOOST_CONTRACT_DETAIL_PP_KEYWORD_REMOVE_PUBLIC(tokens) \
+    BOOST_PP_CAT(BOOST_CONTRACT_DETAIL_PP_KEYWORD_PUBLIC_CAT_TO_EMPTY, tokens)
+
+#endif // #include guard
+

install/boost_1_75_0/include/boost/contract/detail/preprocessor/keyword/utility/is.hpp

@@ -0,0 +1,30 @@
+
+#ifndef BOOST_CONTRACT_DETAIL_PP_KEYWORD_UTILITY_IS_HPP_
+#define BOOST_CONTRACT_DETAIL_PP_KEYWORD_UTILITY_IS_HPP_
+
+// Copyright (C) 2008-2018 Lorenzo Caminiti
+// Distributed under the Boost Software License, Version 1.0 (see accompanying
+// file LICENSE_1_0.txt or a copy at http://www.boost.org/LICENSE_1_0.txt).
+// See: http://www.boost.org/doc/libs/release/libs/contract/doc/html/index.html
+
+#include <boost/preprocessor/cat.hpp>
+#include <boost/preprocessor/variadic/size.hpp>
+
+/* PRIVATE */
+
+#define BOOST_CONTRACT_DETAIL_PP_KEYWORD_UTILITY_IS_1 0
+#define BOOST_CONTRACT_DETAIL_PP_KEYWORD_UTILITY_IS_2 1
+
+/* PUBLIC */
+
+// Precondition: A macro named `cat_to_comma_prefix ## token-to-check` must be
+//               #defined to expand to `,`.
+// Precondition: tokens must start with a token concatenable to a macro name
+//               (e.g., a literal or integral token).
+#define BOOST_CONTRACT_DETAIL_PP_KEYWORD_UTILITY_IS( \
+        cat_to_comma_prefix, tokens) \
+    BOOST_PP_CAT(BOOST_CONTRACT_DETAIL_PP_KEYWORD_UTILITY_IS_, \
+            BOOST_PP_VARIADIC_SIZE(BOOST_PP_CAT(cat_to_comma_prefix, tokens)))
+
+#endif // #include guard
+

install/boost_1_75_0/include/boost/contract/detail/preprocessor/keyword/virtual.hpp

@@ -0,0 +1,35 @@
+
+#ifndef BOOST_CONTRACT_DETAIL_PP_KEYWORD_VIRTUAL_HPP_
+#define BOOST_CONTRACT_DETAIL_PP_KEYWORD_VIRTUAL_HPP_
+
+// Copyright (C) 2008-2018 Lorenzo Caminiti
+// Distributed under the Boost Software License, Version 1.0 (see accompanying
+// file LICENSE_1_0.txt or a copy at http://www.boost.org/LICENSE_1_0.txt).
+// See: http://www.boost.org/doc/libs/release/libs/contract/doc/html/index.html
+
+#include <boost/contract/detail/preprocessor/keyword/utility/is.hpp>
+#include <boost/preprocessor/cat.hpp>
+
+/* PRIVATE */
+
+// Must expand to a single comma `,` (not local macros, do not #undefine).
+#define BOOST_CONTRACT_DETAIL_PP_KEYWORD_VIRTUAL_CAT_TO_COMMAvirtual ,
+
+// Must expand to empty `` (not local macros, do not #undefine).
+#define BOOST_CONTRACT_DETAIL_PP_KEYWORD_VIRTUAL_CAT_TO_EMPTYvirtual
+
+/* PUBLIC */
+
+// Precondition: tokens must start with a token concatenable to a macro name
+//               (e.g., a literal or integral token).
+#define BOOST_CONTRACT_DETAIL_PP_KEYWORD_IS_VIRTUAL(tokens) \
+    BOOST_CONTRACT_DETAIL_PP_KEYWORD_UTILITY_IS( \
+            BOOST_CONTRACT_DETAIL_PP_KEYWORD_VIRTUAL_CAT_TO_COMMA, tokens)
+
+// Precondition: tokens must start with `virtual` (this can be
+//               checked with `..._IS_VIRTUAL` macro above).
+#define BOOST_CONTRACT_DETAIL_PP_KEYWORD_REMOVE_VIRTUAL(tokens) \
+    BOOST_PP_CAT(BOOST_CONTRACT_DETAIL_PP_KEYWORD_VIRTUAL_CAT_TO_EMPTY, tokens)
+
+#endif // #include guard
+

install/boost_1_75_0/include/boost/contract/detail/static_local_var.hpp

@@ -0,0 +1,41 @@
+
+#ifndef BOOST_CONTRACT_DETAIL_STATIC_LOCAL_VAR_HPP_
+#define BOOST_CONTRACT_DETAIL_STATIC_LOCAL_VAR_HPP_
+
+// Copyright (C) 2008-2018 Lorenzo Caminiti
+// Distributed under the Boost Software License, Version 1.0 (see accompanying
+// file LICENSE_1_0.txt or a copy at http://www.boost.org/LICENSE_1_0.txt).
+// See: http://www.boost.org/doc/libs/release/libs/contract/doc/html/index.html
+
+namespace boost { namespace contract { namespace detail {
+
+// This is used to hold the state of this library (already checking assertions,
+// failure handers, mutexes, etc.). Local static variables are used instead of
+// global or class-level static variables to avoid ODR errors when this library
+// is used as header-only.
+
+// Use T's default constructor to init the local var.
+template<typename Tag, typename T>
+struct static_local_var {
+    static T& ref() {
+        static T data;
+        return data;
+    }
+};
+
+// Use `init` param to init local var (Init same as or convertible to T).
+// NOTE: Template specializations could be used to program both this and the
+// template above together but some pre-C++11 compilers give errors (e.g., Clang
+// without -std=c++11), plus the `_init` postfix is more readable at call site.
+template<typename Tag, typename T, typename Init, Init init>
+struct static_local_var_init {
+    static T& ref() {
+        static T data = init;
+        return data;
+    }
+};
+
+} } } // namespace
+       
+#endif // #include guard
+

install/boost_1_75_0/include/boost/contract/detail/tvariadic.hpp

@@ -0,0 +1,190 @@
+
+#ifndef BOOST_CONTRACT_DETAIL_TVARIADIC_HPP_
+#define BOOST_CONTRACT_DETAIL_TVARIADIC_HPP_
+
+// Copyright (C) 2008-2018 Lorenzo Caminiti
+// Distributed under the Boost Software License, Version 1.0 (see accompanying
+// file LICENSE_1_0.txt or a copy at http://www.boost.org/LICENSE_1_0.txt).
+// See: http://www.boost.org/doc/libs/release/libs/contract/doc/html/index.html
+
+#include <boost/config.hpp>
+#ifdef BOOST_NO_CXX11_VARIADIC_TEMPLATES
+    #define BOOST_CONTRACT_DETAIL_TVARIADIC 0
+#else
+    #define BOOST_CONTRACT_DETAIL_TVARIADIC 1
+#endif
+
+#if BOOST_CONTRACT_DETAIL_TVARIADIC
+    #include <tuple>
+
+    /* CODE */
+
+    namespace boost { namespace contract { namespace detail {
+            namespace tvariadic_ {
+        template<int...> struct indexes {};
+
+        template<int N, int... I> struct indexes_of :
+                indexes_of<N - 1, N - 1, I...> {};
+        template<int... I> struct indexes_of<0, I...>
+                { typedef indexes<I...> type; };
+    } } } } // namespace
+
+#else
+    #include <boost/preprocessor/repetition/enum.hpp>
+    #include <boost/preprocessor/repetition/repeat.hpp>
+    #include <boost/preprocessor/tuple/elem.hpp>
+    #include <boost/preprocessor/punctuation/comma_if.hpp>
+    #include <boost/preprocessor/cat.hpp>
+
+    /* PRIVATE */
+
+    #define BOOST_CONTRACT_DETAIL_TVARIADIC_TUPLE_ELEM_(z, n, tuple) \
+        BOOST_PP_CAT(tuple, n)
+    
+    #define BOOST_CONTRACT_DETAIL_TVARIADIC_TUPLE_INIT_(z, n, tuplevar_values) \
+        BOOST_PP_CAT(BOOST_PP_TUPLE_ELEM(2, 0, tuplevar_values), n)( \
+                BOOST_PP_CAT(BOOST_PP_TUPLE_ELEM(2, 1, tuplevar_values), n))
+
+    #define BOOST_CONTRACT_DETAIL_TVARIADIC_TUPLE_(z, n, type_qualifier_name) \
+        BOOST_PP_CAT(BOOST_PP_TUPLE_ELEM(3, 0, type_qualifier_name), n) \
+            BOOST_PP_TUPLE_ELEM(3, 1, type_qualifier_name) \
+            BOOST_PP_CAT(BOOST_PP_TUPLE_ELEM(3, 2, type_qualifier_name), n) \
+        ;
+
+    #define BOOST_CONTRACT_DETAIL_NO_TVARIADIC_ENUM_(z, n, tokens) \
+        tokens
+     
+    #define BOOST_CONTRACT_DETAIL_TVARIADIC_ARG_(z, n, name) \
+        BOOST_PP_CAT(name, n)
+    
+    #define BOOST_CONTRACT_DETAIL_TVARIADIC_FPARAM_(z, n, type_qualifier_name) \
+        BOOST_PP_CAT(BOOST_PP_TUPLE_ELEM(3, 0, type_qualifier_name), n) \
+        BOOST_PP_TUPLE_ELEM(3, 1, type_qualifier_name) \
+        BOOST_PP_CAT(BOOST_PP_TUPLE_ELEM(3, 2, type_qualifier_name), n)
+    
+    #define BOOST_CONTRACT_DETAIL_TVARIADIC_TPARAM_(z, n, name) \
+        typename BOOST_PP_CAT(name, n)
+#endif
+
+/* PUBLIC */
+
+#if BOOST_CONTRACT_DETAIL_TVARIADIC
+    #define BOOST_CONTRACT_DETAIL_TVARIADIC_COMMA(arity) \
+        ,
+#else
+    #define BOOST_CONTRACT_DETAIL_TVARIADIC_COMMA(arity) \
+        BOOST_PP_COMMA_IF(arity)
+#endif
+
+#if BOOST_CONTRACT_DETAIL_TVARIADIC
+    #define BOOST_CONTRACT_DETAIL_NO_TVARIADIC_COMMA(arity) /* nothing */
+#else
+    #define BOOST_CONTRACT_DETAIL_NO_TVARIADIC_COMMA(arity) \
+        BOOST_PP_COMMA_IF(arity)
+#endif
+
+#if BOOST_CONTRACT_DETAIL_TVARIADIC
+    #define BOOST_CONTRACT_DETAIL_TVARIADIC_SIZEOF(arity, name) sizeof...(name)
+#else
+    #define BOOST_CONTRACT_DETAIL_TVARIADIC_SIZEOF(arity, name) arity
+#endif
+
+#if BOOST_CONTRACT_DETAIL_TVARIADIC
+    #define BOOST_CONTRACT_DETAIL_TVARIADIC_TPARAMS_Z(z, arity, name) \
+        typename... name
+#else
+    #define BOOST_CONTRACT_DETAIL_TVARIADIC_TPARAMS_Z(z, arity, name) \
+        BOOST_PP_ENUM_ ## z(arity, BOOST_CONTRACT_DETAIL_TVARIADIC_TPARAM_, \
+                name)
+#endif
+
+#if BOOST_CONTRACT_DETAIL_TVARIADIC
+    #define BOOST_CONTRACT_DETAIL_TVARIADIC_FPARAMS_Z( \
+            z, arity, type, qualifier, name) \
+        type qualifier ... name
+#else
+    #define BOOST_CONTRACT_DETAIL_TVARIADIC_FPARAMS_Z( \
+            z, arity, type, qualifier, name) \
+        BOOST_PP_ENUM_ ## z(arity, BOOST_CONTRACT_DETAIL_TVARIADIC_FPARAM_, \
+                (type, qualifier, name))
+#endif
+
+#if BOOST_CONTRACT_DETAIL_TVARIADIC
+    #define BOOST_CONTRACT_DETAIL_TVARIADIC_ARGS_Z(z, arity, name) \
+        name...
+#else
+    #define BOOST_CONTRACT_DETAIL_TVARIADIC_ARGS_Z(z, arity, name) \
+        BOOST_PP_ENUM_ ## z(arity, BOOST_CONTRACT_DETAIL_TVARIADIC_ARG_, name)
+#endif
+
+#if BOOST_CONTRACT_DETAIL_TVARIADIC
+    #define BOOST_CONTRACT_DETAIL_NO_TVARIADIC_ENUM_Z(z, arity, tokens) \
+        /* nothing */
+#else
+    #define BOOST_CONTRACT_DETAIL_NO_TVARIADIC_ENUM_Z(z, arity, tokens) \
+        BOOST_PP_ENUM_ ## z(arity, BOOST_CONTRACT_DETAIL_NO_TVARIADIC_ENUM_, \
+                tokens)
+#endif
+
+// Tuple.
+
+#if BOOST_CONTRACT_DETAIL_TVARIADIC
+    #define BOOST_CONTRACT_DETAIL_TVARIADIC_TUPLE_Z( \
+            z, arity, type, qualifier, name) \
+        std::tuple<type qualifier ...> name;
+#else
+    #define BOOST_CONTRACT_DETAIL_TVARIADIC_TUPLE_Z( \
+            z, arity, type, qualifier, name) \
+        BOOST_PP_REPEAT_ ## z(arity, BOOST_CONTRACT_DETAIL_TVARIADIC_TUPLE_, \
+                (type, qualifier, name))
+#endif
+
+#if BOOST_CONTRACT_DETAIL_TVARIADIC
+    #define BOOST_CONTRACT_DETAIL_TVARIADIC_TUPLE_INIT_Z(z, \
+            arity, tuple, values) \
+        tuple(values...)
+#else
+    #define BOOST_CONTRACT_DETAIL_TVARIADIC_TUPLE_INIT_Z(z, \
+            arity, tuple, values) \
+        BOOST_PP_ENUM_ ## z(arity, BOOST_CONTRACT_DETAIL_TVARIADIC_TUPLE_INIT_,\
+                (tuple, values))
+#endif
+
+#if BOOST_CONTRACT_DETAIL_TVARIADIC
+    #define BOOST_CONTRACT_DETAIL_TVARIADIC_TUPLE_INDEXES_TPARAM(indexes) \
+        int... indexes
+#else
+    #define BOOST_CONTRACT_DETAIL_TVARIADIC_TUPLE_INDEXES_TPARAM(indexes) \
+        /* nothing */
+#endif
+
+#if BOOST_CONTRACT_DETAIL_TVARIADIC
+    #define BOOST_CONTRACT_DETAIL_TVARIADIC_TUPLE_INDEXES_FPARAM(_indexes) \
+        boost::contract::detail::tvariadic_::indexes<_indexes...>
+#else
+    #define BOOST_CONTRACT_DETAIL_TVARIADIC_TUPLE_INDEXES_FPARAM(_indexes) \
+        /* nothing */
+#endif
+
+#if BOOST_CONTRACT_DETAIL_TVARIADIC
+    #define BOOST_CONTRACT_DETAIL_TVARIADIC_TUPLE_INDEXES_OF(tuple_type) \
+        typename boost::contract::detail::tvariadic_::indexes_of< \
+                sizeof...(tuple_type)>::type()
+#else
+    #define BOOST_CONTRACT_DETAIL_TVARIADIC_TUPLE_INDEXES_OF(unused) \
+        /* nothing */
+#endif
+
+#if BOOST_CONTRACT_DETAIL_TVARIADIC
+    #define BOOST_CONTRACT_DETAIL_TVARIADIC_TUPLE_ELEMS_Z( \
+            z, arity, indexes, tuple) \
+        std::get<indexes>(tuple)...
+#else
+    #define BOOST_CONTRACT_DETAIL_TVARIADIC_TUPLE_ELEMS_Z( \
+            z, arity, indexes, tuple) \
+        BOOST_PP_ENUM_ ## z(arity, BOOST_CONTRACT_DETAIL_TVARIADIC_TUPLE_ELEM_,\
+                tuple)
+#endif
+
+#endif // #include guard
+

install/boost_1_75_0/include/boost/contract/detail/type_traits/member_function_types.hpp

@@ -0,0 +1,72 @@
+
+#ifndef BOOST_CONTRACT_DETAIL_MEMBER_FUNCTION_TYPES_HPP_
+#define BOOST_CONTRACT_DETAIL_MEMBER_FUNCTION_TYPES_HPP_
+
+// Copyright (C) 2008-2018 Lorenzo Caminiti
+// Distributed under the Boost Software License, Version 1.0 (see accompanying
+// file LICENSE_1_0.txt or a copy at http://www.boost.org/LICENSE_1_0.txt).
+// See: http://www.boost.org/doc/libs/release/libs/contract/doc/html/index.html
+
+#include <boost/contract/detail/none.hpp>
+#include <boost/function_types/parameter_types.hpp>
+#include <boost/function_types/result_type.hpp>
+#include <boost/function_types/property_tags.hpp>
+#include <boost/type_traits/is_const.hpp>
+#include <boost/type_traits/is_volatile.hpp>
+#include <boost/type_traits/is_same.hpp>
+#include <boost/mpl/pop_front.hpp>
+#include <boost/mpl/push_back.hpp>
+#include <boost/mpl/back.hpp>
+#include <boost/mpl/and.hpp>
+#include <boost/mpl/if.hpp>
+#include <boost/mpl/identity.hpp>
+
+namespace boost {
+    namespace contract {
+        class virtual_;
+    }
+}
+
+namespace boost { namespace contract { namespace detail {
+
+template<class C, typename F>
+struct member_function_types {
+    typedef typename boost::function_types::result_type<F>::type result_type;
+
+    // Never include leading class type.
+    typedef typename boost::mpl::pop_front<typename boost::function_types::
+            parameter_types<F>::type>::type argument_types;
+
+    // Always include trailing virtual_* type.
+    typedef typename boost::mpl::if_<boost::is_same<typename boost::
+            mpl::back<argument_types>::type, boost::contract::virtual_*>,
+        boost::mpl::identity<argument_types>
+    ,
+        boost::mpl::push_back<argument_types, boost::contract::virtual_*>
+    >::type::type virtual_argument_types;
+
+    typedef typename boost::mpl::if_<boost::mpl::and_<boost::is_const<C>,
+            boost::is_volatile<C> >,
+        boost::function_types::cv_qualified
+    , typename boost::mpl::if_<boost::is_const<C>,
+        boost::function_types::const_non_volatile
+    , typename boost::mpl::if_<boost::is_volatile<C>,
+        boost::function_types::volatile_non_const
+    ,
+        boost::function_types::null_tag
+    >::type>::type>::type property_tag;
+};
+
+// Also handles none type.
+template<class C>
+struct member_function_types<C, none> {
+    typedef none result_type;
+    typedef none argument_types;
+    typedef none virtual_argument_types;
+    typedef none property_tag;
+};
+
+} } } // namespace
+
+#endif // #include guard
+

install/boost_1_75_0/include/boost/contract/detail/type_traits/mirror.hpp

@@ -0,0 +1,111 @@
+
+#ifndef BOOST_CONTRACT_DETAIL_MIRROR_HPP_
+#define BOOST_CONTRACT_DETAIL_MIRROR_HPP_
+
+// Copyright (C) 2008-2018 Lorenzo Caminiti
+// Distributed under the Boost Software License, Version 1.0 (see accompanying
+// file LICENSE_1_0.txt or a copy at http://www.boost.org/LICENSE_1_0.txt).
+// See: http://www.boost.org/doc/libs/release/libs/contract/doc/html/index.html
+
+#include <boost/contract/detail/name.hpp>
+#include <boost/function_types/member_function_pointer.hpp>
+#include <boost/function_types/function_pointer.hpp>
+#include <boost/function_types/property_tags.hpp>
+#include <boost/mpl/push_front.hpp>
+#include <boost/mpl/bool.hpp>
+#include <boost/preprocessor/control/iif.hpp>
+#include <boost/preprocessor/tuple/rem.hpp>
+#include <boost/preprocessor/tuple/eat.hpp>
+
+// NOTE: Unfortunately, it is not possible to use Boost.TTI because it not
+// always works on MSVC (e.g., when the mirror meta-function is invoked
+// multiple times, MSVC 2010 gives an internal compiler error). This is a
+// simpler mirror implementation that seems to work better on MSVC.
+
+/* PRIVATE */
+
+#define BOOST_CONTRACT_DETAIL_MIRROR_END_(tparam) \
+        template<typename> \
+        static boost::contract::detail::mirror::no& apply(...); \
+    public: \
+        static bool const value = sizeof(apply<tparam>(0)) == \
+                sizeof(boost::contract::detail::mirror::yes); \
+        typedef boost::mpl::bool_<value> type;
+
+#define BOOST_CONTRACT_DETAIL_MIRROR_HAS_MEMBER_FUNCTION_(is_static, \
+        trait, func_name) \
+    template< \
+        typename BOOST_CONTRACT_DETAIL_NAME1(T), \
+        typename BOOST_CONTRACT_DETAIL_NAME1(R), \
+        class BOOST_CONTRACT_DETAIL_NAME1(P), \
+        class BOOST_CONTRACT_DETAIL_NAME1(G) = boost::function_types::null_tag \
+    > \
+    class trait { \
+        template<class BOOST_CONTRACT_DETAIL_NAME1(C)> \
+        static boost::contract::detail::mirror::yes& apply( \
+            boost::contract::detail::mirror::check_function< \
+                typename \
+                    BOOST_PP_IIF(is_static, \
+                        boost::function_types::function_pointer \
+                    , \
+                        boost::function_types::member_function_pointer \
+                    ) \
+                < \
+                    typename boost::mpl::push_front< \
+                        BOOST_PP_IIF(is_static, \
+                            BOOST_CONTRACT_DETAIL_NAME1(P) \
+                            BOOST_PP_TUPLE_EAT(2) \
+                        , \
+                            BOOST_PP_TUPLE_REM(2) \
+                        )( \
+                            typename boost::mpl::push_front< \
+                                BOOST_CONTRACT_DETAIL_NAME1(P), \
+                                BOOST_CONTRACT_DETAIL_NAME1(C) \
+                            >::type \
+                        ) \
+                        , BOOST_CONTRACT_DETAIL_NAME1(R) \
+                    >::type, \
+                    BOOST_CONTRACT_DETAIL_NAME1(G) \
+                >::type, \
+                &BOOST_CONTRACT_DETAIL_NAME1(C)::func_name \
+            >* \
+        ); \
+        BOOST_CONTRACT_DETAIL_MIRROR_END_( \
+                BOOST_CONTRACT_DETAIL_NAME1(T)) \
+    };
+
+/* PUBLIC */
+
+#define BOOST_CONTRACT_DETAIL_MIRROR_HAS_TYPE(trait, type_name)\
+    template<typename BOOST_CONTRACT_DETAIL_NAME1(T)> \
+    class trait { \
+        template<class BOOST_CONTRACT_DETAIL_NAME1(C)> \
+        static boost::contract::detail::mirror::yes& apply( \
+                typename BOOST_CONTRACT_DETAIL_NAME1(C)::type_name*); \
+        BOOST_CONTRACT_DETAIL_MIRROR_END_( \
+                BOOST_CONTRACT_DETAIL_NAME1(T)) \
+    };
+
+#define BOOST_CONTRACT_DETAIL_MIRROR_HAS_MEMBER_FUNCTION( \
+        trait, func_name) \
+    BOOST_CONTRACT_DETAIL_MIRROR_HAS_MEMBER_FUNCTION_( \
+            /* is_static = */ 0, trait, func_name)
+
+#define BOOST_CONTRACT_DETAIL_MIRROR_HAS_STATIC_MEMBER_FUNCTION(trait, \
+        func_name) \
+    BOOST_CONTRACT_DETAIL_MIRROR_HAS_MEMBER_FUNCTION_( \
+            /* is_static = */ 1, trait, func_name)
+        
+/* CODE */
+
+namespace boost { namespace contract { namespace detail { namespace mirror {
+
+typedef class {} yes;
+typedef yes no[2];
+
+template<typename F, F> class check_function;
+
+} } } } // namespace
+
+#endif // #include guard
+

install/boost_1_75_0/include/boost/contract/detail/type_traits/optional.hpp

@@ -0,0 +1,42 @@
+
+#ifndef BOOST_CONTRACT_DETAIL_OPTIONAL_HPP_
+#define BOOST_CONTRACT_DETAIL_OPTIONAL_HPP_
+
+// Copyright (C) 2008-2018 Lorenzo Caminiti
+// Distributed under the Boost Software License, Version 1.0 (see accompanying
+// file LICENSE_1_0.txt or a copy at http://www.boost.org/LICENSE_1_0.txt).
+// See: http://www.boost.org/doc/libs/release/libs/contract/doc/html/index.html
+
+#include <boost/optional.hpp>
+#include <boost/type_traits/remove_reference.hpp>
+#include <boost/type_traits/integral_constant.hpp>
+
+namespace boost { namespace contract { namespace detail {
+
+template<typename T>
+struct is_optional : boost::false_type {};
+template<typename T>
+struct is_optional<boost::optional<T> > : boost::true_type {};
+
+template<typename T>
+struct optional_value_type { typedef T type; };
+template<typename T>
+struct optional_value_type<boost::optional<T> > { typedef T type; };
+
+template<typename T>
+struct remove_value_reference_if_optional { typedef T type; };
+template<typename T>
+struct remove_value_reference_if_optional<boost::optional<T> >
+        { typedef typename boost::remove_reference<T>::type type; };
+
+template<typename T>
+T& optional_get(T& x) { return x; }
+template<typename T>
+T& optional_get(boost::optional<T>& x) { return x.get(); }
+template<typename T>
+T& optional_get(boost::optional<T&>& x) { return x.get(); }
+
+} } } // namespace
+
+#endif // #include guard
+