binders.h

Go to the documentation of this file.

// Functor implementations -*- C++ -*-

// Copyright (C) 2001, 2002, 2003, 2004, 2005, 2006, 2007
// Free Software Foundation, Inc.
//
// This file is part of the GNU ISO C++ Library.  This library is free
// software; you can redistribute it and/or modify it under the
// terms of the GNU General Public License as published by the
// Free Software Foundation; either version 2, or (at your option)
// any later version.

// This library is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU General Public License for more details.

// You should have received a copy of the GNU General Public License along
// with this library; see the file COPYING.  If not, write to the Free
// Software Foundation, 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301,
// USA.

// As a special exception, you may use this file as part of a free software
// library without restriction.  Specifically, if other files instantiate
// templates or use macros or inline functions from this file, or you compile
// this file and link it with other files to produce an executable, this
// file does not by itself cause the resulting executable to be covered by
// the GNU General Public License.  This exception does not however
// invalidate any other reasons why the executable file might be covered by
// the GNU General Public License.

/*
 *
 * Copyright (c) 1994
 * Hewlett-Packard Company
 *
 * Permission to use, copy, modify, distribute and sell this software
 * and its documentation for any purpose is hereby granted without fee,
 * provided that the above copyright notice appear in all copies and
 * that both that copyright notice and this permission notice appear
 * in supporting documentation.  Hewlett-Packard Company makes no
 * representations about the suitability of this software for any
 * purpose.  It is provided "as is" without express or implied warranty.
 *
 *
 * Copyright (c) 1996-1998
 * Silicon Graphics Computer Systems, Inc.
 *
 * Permission to use, copy, modify, distribute and sell this software
 * and its documentation for any purpose is hereby granted without fee,
 * provided that the above copyright notice appear in all copies and
 * that both that copyright notice and this permission notice appear
 * in supporting documentation.  Silicon Graphics makes no
 * representations about the suitability of this software for any
 * purpose.  It is provided "as is" without express or implied warranty.
 */

/** @file backward/binders.h
 *  This is an internal header file, included by other library headers.
 *  You should not attempt to use it directly.
 */

#ifndef _GLIBCXX_BINDERS_H
#define _GLIBCXX_BINDERS_H 1

_GLIBCXX_BEGIN_NAMESPACE(std)

  // 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, a 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<typename _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); }
    } _GLIBCXX_DEPRECATED_ATTR;

  /// One of the @link s20_3_6_binder binder functors@endlink.
  template<typename _Operation, typename _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<typename _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); }
    } _GLIBCXX_DEPRECATED_ATTR;

  /// One of the @link s20_3_6_binder binder functors@endlink.
  template<typename _Operation, typename _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));
    } 
  /** @}  */

_GLIBCXX_END_NAMESPACE

#endif /* _GLIBCXX_BINDERS_H */

---