stl_function.h

来自「symbian上STL模板库的实现」· C头文件 代码 · 共 899 行 · 第 1/3 页

     *  The call to @c find_if will locate the first index (i) of @c v for which
     *  "!(v[i] > 3)" is true.
     *
     *  The not1/unary_negate combination works on predicates taking a single
     *  argument.  The not2/binary_negate combination works on predicates which
     *  take two arguments.
     *
     *  @{
     */
    /// One of the @link s20_3_5_negators negation functors@endlink.
    template <class _Predicate>
        class unary_negate
        : public unary_function<typename _Predicate::argument_type, bool>
        {
            protected:
                _Predicate _M_pred;
            public:
                explicit
                    unary_negate(const _Predicate& __x) : _M_pred(__x) {}

                bool
                    operator()(const typename _Predicate::argument_type& __x) const
                    { return !_M_pred(__x); }
        };

    /// One of the @link s20_3_5_negators negation functors@endlink.
    template <class _Predicate>
        inline unary_negate<_Predicate>
        not1(const _Predicate& __pred)
        { return unary_negate<_Predicate>(__pred); }

    /// One of the @link s20_3_5_negators negation functors@endlink.
    template <class _Predicate>
        class binary_negate
        : public binary_function<typename _Predicate::first_argument_type,
        typename _Predicate::second_argument_type,
        bool>
    {
        protected:
            _Predicate _M_pred;
        public:
            explicit
                binary_negate(const _Predicate& __x)
                : _M_pred(__x) { }

            bool
                operator()(const typename _Predicate::first_argument_type& __x,
                        const typename _Predicate::second_argument_type& __y) const
                { return !_M_pred(__x, __y); }
    };

    /// One of the @link s20_3_5_negators negation functors@endlink.
    template <class _Predicate>
        inline binary_negate<_Predicate>
        not2(const _Predicate& __pred)
        { return binary_negate<_Predicate>(__pred); }
    /** @}  */

    // 20.3.6 binders
    /** @defgroup s20_3_6_binder Binder Classes
     *  Binders turn functions/functors with two arguments into functors with
     *  a single argument, storing an argument to be applied later.  For
     *  example, an variable @c B of type @c binder1st is constructed from a
     *  functor @c f and an argument @c x.  Later, B's @c operator() is called
     *  with a single argument @c y.  The return value is the value of @c f(x,y).
     *  @c B can be "called" with various arguments (y1, y2, ...) and will in
     *  turn call @c f(x,y1), @c f(x,y2), ...
     *
     *  The function @c bind1st is provided to save some typing.  It takes the
     *  function and an argument as parameters, and returns an instance of
     *  @c binder1st.
     *
     *  The type @c binder2nd and its creator function @c bind2nd do the same
     *  thing, but the stored argument is passed as the second parameter instead
     *  of the first, e.g., @c bind2nd(std::minus<float>,1.3) will create a
     *  functor whose @c operator() accepts a floating-point number, subtracts
     *  1.3 from it, and returns the result.  (If @c bind1st had been used,
     *  the functor would perform "1.3 - x" instead.
     *
     *  Creator-wrapper functions like @c bind1st are intended to be used in
     *  calling algorithms.  Their return values will be temporary objects.
     *  (The goal is to not require you to type names like
     *  @c std::binder1st<std::plus<int>> for declaring a variable to hold the
     *  return value from @c bind1st(std::plus<int>,5).
     *
     *  These become more useful when combined with the composition functions.
     *
     *  @{
     */
    /// One of the @link s20_3_6_binder binder functors@endlink.
    template <class _Operation>
        class binder1st
        : public unary_function<typename _Operation::second_argument_type,
        typename _Operation::result_type>
    {
        protected:
            _Operation op;
            typename _Operation::first_argument_type value;
        public:
            binder1st(const _Operation& __x,
                    const typename _Operation::first_argument_type& __y)
                : op(__x), value(__y) {}

            typename _Operation::result_type
                operator()(const typename _Operation::second_argument_type& __x) const
                { return op(value, __x); }

            // _GLIBCXX_RESOLVE_LIB_DEFECTS
            // 109.  Missing binders for non-const sequence elements
            typename _Operation::result_type
                operator()(typename _Operation::second_argument_type& __x) const
                { return op(value, __x); }
    };

    /// One of the @link s20_3_6_binder binder functors@endlink.
    template <class _Operation, class _Tp>
        inline binder1st<_Operation>
        bind1st(const _Operation& __fn, const _Tp& __x)
        {
            typedef typename _Operation::first_argument_type _Arg1_type;
            return binder1st<_Operation>(__fn, _Arg1_type(__x));
        }

    /// One of the @link s20_3_6_binder binder functors@endlink.
    template <class _Operation>
        class binder2nd
        : public unary_function<typename _Operation::first_argument_type,
        typename _Operation::result_type>
    {
        protected:
            _Operation op;
            typename _Operation::second_argument_type value;
        public:
            binder2nd(const _Operation& __x,
                    const typename _Operation::second_argument_type& __y)
                : op(__x), value(__y) {}

            typename _Operation::result_type
                operator()(const typename _Operation::first_argument_type& __x) const
                { return op(__x, value); }

            // _GLIBCXX_RESOLVE_LIB_DEFECTS
            // 109.  Missing binders for non-const sequence elements
            typename _Operation::result_type
                operator()(typename _Operation::first_argument_type& __x) const
                { return op(__x, value); }
    };

    /// One of the @link s20_3_6_binder binder functors@endlink.
    template <class _Operation, class _Tp>
        inline binder2nd<_Operation>
        bind2nd(const _Operation& __fn, const _Tp& __x)
        {
            typedef typename _Operation::second_argument_type _Arg2_type;
            return binder2nd<_Operation>(__fn, _Arg2_type(__x));
        }
    /** @}  */

    // 20.3.7 adaptors pointers functions
    /** @defgroup s20_3_7_adaptors Adaptors for pointers to functions
     *  The advantage of function objects over pointers to functions is that
     *  the objects in the standard library declare nested typedefs describing
     *  their argument and result types with uniform names (e.g., @c result_type
     *  from the base classes @c unary_function and @c binary_function).
     *  Sometimes those typedefs are required, not just optional.
     *
     *  Adaptors are provided to turn pointers to unary (single-argument) and
     *  binary (double-argument) functions into function objects.  The
     *  long-winded functor @c pointer_to_unary_function is constructed with a
     *  function pointer @c f, and its @c operator() called with argument @c x
     *  returns @c f(x).  The functor @c pointer_to_binary_function does the same
     *  thing, but with a double-argument @c f and @c operator().
     *
     *  The function @c ptr_fun takes a pointer-to-function @c f and constructs
     *  an instance of the appropriate functor.
     *
     *  @{
     */
    /// One of the @link s20_3_7_adaptors adaptors for function pointers@endlink.
    template <class _Arg, class _Result>
        class pointer_to_unary_function : public unary_function<_Arg, _Result>
    {
        protected:
            _Result (*_M_ptr)(_Arg);
        public:
            pointer_to_unary_function() {}

            explicit
                pointer_to_unary_function(_Result (*__x)(_Arg))
                : _M_ptr(__x) {}

            _Result
                operator()(_Arg __x) const
                { return _M_ptr(__x); }
    };

    /// One of the @link s20_3_7_adaptors adaptors for function pointers@endlink.
    template <class _Arg, class _Result>
        inline pointer_to_unary_function<_Arg, _Result>
        ptr_fun(_Result (*__x)(_Arg))
        { return pointer_to_unary_function<_Arg, _Result>(__x); }

    /// One of the @link s20_3_7_adaptors adaptors for function pointers@endlink.
    template <class _Arg1, class _Arg2, class _Result>
        class pointer_to_binary_function
        : public binary_function<_Arg1, _Arg2, _Result>
        {
            protected:
                _Result (*_M_ptr)(_Arg1, _Arg2);
            public:
                pointer_to_binary_function() {}

                explicit
                    pointer_to_binary_function(_Result (*__x)(_Arg1, _Arg2))
                    : _M_ptr(__x) {}

                _Result
                    operator()(_Arg1 __x, _Arg2 __y) const
                    { return _M_ptr(__x, __y); }
        };

    /// One of the @link s20_3_7_adaptors adaptors for function pointers@endlink.
    template <class _Arg1, class _Arg2, class _Result>
        inline pointer_to_binary_function<_Arg1, _Arg2, _Result>
        ptr_fun(_Result (*__x)(_Arg1, _Arg2))
        { return pointer_to_binary_function<_Arg1, _Arg2, _Result>(__x); }
    /** @}  */

    template <class _Tp>
        struct _Identity : public unary_function<_Tp,_Tp>
    {
        _Tp&
            operator()(_Tp& __x) const
            { return __x; }

        const _Tp&
            operator()(const _Tp& __x) const
            { return __x; }
    };

    template <class _Pair>
        struct _Select1st : public unary_function<_Pair,
        typename _Pair::first_type>
    {
        typename _Pair::first_type&
            operator()(_Pair& __x) const
            { return __x.first; }

        const typename _Pair::first_type&
            operator()(const _Pair& __x) const
            { return __x.first; }
    };

    template <class _Pair>
        struct _Select2nd : public unary_function<_Pair,
        typename _Pair::second_type>
    {
        typename _Pair::second_type&
            operator()(_Pair& __x) const
            { return __x.second; }

        const typename _Pair::second_type&
            operator()(const _Pair& __x) const
            { return __x.second; }
    };

    // 20.3.8 adaptors pointers members
    /** @defgroup s20_3_8_memadaptors Adaptors for pointers to members
     *  There are a total of 16 = 2^4 function objects in this family.
     *   (1) Member functions taking no arguments vs member functions taking
     *        one argument.
     *   (2) Call through pointer vs call through reference.
     *   (3) Member function with void return type vs member function with
     *       non-void return type.
     *   (4) Const vs non-const member function.
     *
     *  Note that choice (3) is nothing more than a workaround: according
     *   to the draft, compilers should handle void and non-void the same way.
     *   This feature is not yet widely implemented, though.  You can only use
     *   member functions returning void if your compiler supports partial
     *   specialization.
     *
     *  All of this complexity is in the function objects themselves.  You can
     *   ignore it by using the helper function mem_fun and mem_fun_ref,
     *   which create whichever type of adaptor is appropriate.
     *
     *  @{
     */
    /// One of the @link s20_3_8_memadaptors adaptors for member pointers@endlink.
    template <class _Ret, class _Tp>
        class mem_fun_t : public unary_function<_Tp*, _Ret>
    {
        public:
            explicit
                mem_fun_t(_Ret (_Tp::*__pf)())
                : _M_f(__pf) {}

            _Ret
                operator()(_Tp* __p) const
                { return (__p->*_M_f)(); }