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// Functional extensions -*- C++ -*-

// Copyright (C) 2002, 2004 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

 * 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 ext/functional

 *  This file is a GNU extension to the Standard C++ Library (possibly

 *  containing extensions from the HP/SGI STL subset).

 */

#ifndef _EXT_FUNCTIONAL

#define _EXT_FUNCTIONAL 1

#pragma GCC system_header

#include 

namespace __gnu_cxx

{

  using std::unary_function;

  using std::binary_function;

  using std::mem_fun1_t;

  using std::const_mem_fun1_t;

  using std::mem_fun1_ref_t;

  using std::const_mem_fun1_ref_t;

  /** The @c identity_element functions are not part of the C++ standard; SGI

   *  provided them as an extension.  Its argument is an operation, and its

   *  return value is the identity element for that operation.  It is overloaded

   *  for addition and multiplication, and you can overload it for your own

   *  nefarious operations.

   *

   *  @addtogroup SGIextensions

   *  @{

   */

  /// An \link SGIextensions SGI extension \endlink.

  template 

    inline _Tp

    identity_element(std::plus<_Tp>)

    { return _Tp(0); }

  /// An \link SGIextensions SGI extension \endlink.

  template 

    inline _Tp

    identity_element(std::multiplies<_Tp>)

    { return _Tp(1); }

  /** @}  */

  /** As an extension to the binders, SGI provided composition functors and

   *  wrapper functions to aid in their creation.  The @c unary_compose

   *  functor is constructed from two functions/functors, @c f and @c g.

   *  Calling @c operator() with a single argument @c x returns @c f(g(x)).

   *  The function @c compose1 takes the two functions and constructs a

   *  @c unary_compose variable for you.

   *

   *  @c binary_compose is constructed from three functors, @c f, @c g1,

   *  and @c g2.  Its @c operator() returns @c f(g1(x),g2(x)).  The function

   *  @compose2 takes f, g1, and g2, and constructs the @c binary_compose

   *  instance for you.  For example, if @c f returns an int, then

   *  \code

   *  int answer = (compose2(f,g1,g2))(x);

   *  \endcode

   *  is equivalent to

   *  \code

   *  int temp1 = g1(x);

   *  int temp2 = g2(x);

   *  int answer = f(temp1,temp2);

   *  \endcode

   *  But the first form is more compact, and can be passed around as a

   *  functor to other algorithms.

   *

   *  @addtogroup SGIextensions

   *  @{

   */

  /// An \link SGIextensions SGI extension \endlink.

  template 

    class unary_compose

    : public unary_function

                            typename _Operation1::result_type>

    {

    protected:

      _Operation1 _M_fn1;

      _Operation2 _M_fn2;

    public:

      unary_compose(const _Operation1& __x, const _Operation2& __y)

      : _M_fn1(__x), _M_fn2(__y) {}

      typename _Operation1::result_type

      operator()(const typename _Operation2::argument_type& __x) const

      { return _M_fn1(_M_fn2(__x)); }

    };

  /// An \link SGIextensions SGI extension \endlink.

  template 

    inline unary_compose<_Operation1, _Operation2>

    compose1(const _Operation1& __fn1, const _Operation2& __fn2)

    { return unary_compose<_Operation1,_Operation2>(__fn1, __fn2); }

  /// An \link SGIextensions SGI extension \endlink.

  template 

    class binary_compose

    : public unary_function

                            typename _Operation1::result_type>

    {

    protected:

      _Operation1 _M_fn1;

      _Operation2 _M_fn2;

      _Operation3 _M_fn3;

    public:

      binary_compose(const _Operation1& __x, const _Operation2& __y,

                     const _Operation3& __z)

      : _M_fn1(__x), _M_fn2(__y), _M_fn3(__z) { }

      typename _Operation1::result_type

      operator()(const typename _Operation2::argument_type& __x) const

      { return _M_fn1(_M_fn2(__x), _M_fn3(__x)); }

    };

  /// An \link SGIextensions SGI extension \endlink.

  template 

    inline binary_compose<_Operation1, _Operation2, _Operation3>

    compose2(const _Operation1& __fn1, const _Operation2& __fn2,

             const _Operation3& __fn3)

    { return binary_compose<_Operation1, _Operation2, _Operation3>

        (__fn1, __fn2, __fn3); }

  /** @}  */

  /** As an extension, SGI provided a functor called @c identity.  When a

   *  functor is required but no operations are desired, this can be used as a

   *  pass-through.  Its @c operator() returns its argument unchanged.

   *

   *  @addtogroup SGIextensions

   */

  template 

    struct identity : public std::_Identity<_Tp> {};

  /** @c select1st and @c select2nd are extensions provided by SGI.  Their

   *  @c operator()s

   *  take a @c std::pair as an argument, and return either the first member

   *  or the second member, respectively.  They can be used (especially with

   *  the composition functors) to "strip" data from a sequence before

   *  performing the remainder of an algorithm.

   *

   *  @addtogroup SGIextensions

   *  @{

   */

  /// An \link SGIextensions SGI extension \endlink.

  template 

    struct select1st : public std::_Select1st<_Pair> {};

  /// An \link SGIextensions SGI extension \endlink.

  template 

    struct select2nd : public std::_Select2nd<_Pair> {};

  /** @}  */

  // extension documented next

  template 

    struct _Project1st : public binary_function<_Arg1, _Arg2, _Arg1>

    {

      _Arg1

      operator()(const _Arg1& __x, const _Arg2&) const

      { return __x; }

    };

  template 

    struct _Project2nd : public binary_function<_Arg1, _Arg2, _Arg2>

    {

      _Arg2

      operator()(const _Arg1&, const _Arg2& __y) const

      { return __y; }

    };

  /** The @c operator() of the @c project1st functor takes two arbitrary

   *  arguments and returns the first one, while @c project2nd returns the

   *  second one.  They are extensions provided by SGI.

   *

   *  @addtogroup SGIextensions

   *  @{

   */

  /// An \link SGIextensions SGI extension \endlink.

  template 

    struct project1st : public _Project1st<_Arg1, _Arg2> {};

  /// An \link SGIextensions SGI extension \endlink.

  template 

    struct project2nd : public _Project2nd<_Arg1, _Arg2> {};

  /** @}  */

  // extension documented next

  template 

    struct _Constant_void_fun

    {

      typedef _Result result_type;

      result_type _M_val;

      _Constant_void_fun(const result_type& __v) : _M_val(__v) {}

      const result_type&

      operator()() const

      { return _M_val; }

    };

  template 

    struct _Constant_unary_fun

    {

      typedef _Argument argument_type;

      typedef  _Result  result_type;

      result_type _M_val;

      _Constant_unary_fun(const result_type& __v) : _M_val(__v) {}

      const result_type&

      operator()(const _Argument&) const

      { return _M_val; }

    };

  template 

    struct _Constant_binary_fun

    {

      typedef  _Arg1   first_argument_type;

      typedef  _Arg2   second_argument_type;

      typedef  _Result result_type;

      _Result _M_val;

      _Constant_binary_fun(const _Result& __v) : _M_val(__v) {}

      const result_type&

      operator()(const _Arg1&, const _Arg2&) const

      { return _M_val; }

    };

  /** These three functors are each constructed from a single arbitrary

   *  variable/value.  Later, their @c operator()s completely ignore any

   *  arguments passed, and return the stored value.

   *  - @c constant_void_fun's @c operator() takes no arguments

   *  - @c constant_unary_fun's @c operator() takes one argument (ignored)

   *  - @c constant_binary_fun's @c operator() takes two arguments (ignored)

   *

   *  The helper creator functions @c constant0, @c constant1, and

   *  @c constant2 each take a "result" argument and construct variables of

   *  the appropriate functor type.

   *

   *  @addtogroup SGIextensions

   *  @{

   */

  /// An \link SGIextensions SGI extension \endlink.

  template 

    struct constant_void_fun

    : public _Constant_void_fun<_Result>

    {

      constant_void_fun(const _Result& __v)

      : _Constant_void_fun<_Result>(__v) {}

    };

  /// An \link SGIextensions SGI extension \endlink.

  template 

    struct constant_unary_fun : public _Constant_unary_fun<_Result, _Argument>

    {

      constant_unary_fun(const _Result& __v)

      : _Constant_unary_fun<_Result, _Argument>(__v) {}

    };

  /// An \link SGIextensions SGI extension \endlink.

  template 

    struct constant_binary_fun

    : public _Constant_binary_fun<_Result, _Arg1, _Arg2>

    {

      constant_binary_fun(const _Result& __v)

      : _Constant_binary_fun<_Result, _Arg1, _Arg2>(__v) {}

    };

  /// An \link SGIextensions SGI extension \endlink.

  template 

    inline constant_void_fun<_Result>

    constant0(const _Result& __val)

    { return constant_void_fun<_Result>(__val); }

  /// An \link SGIextensions SGI extension \endlink.

  template 

    inline constant_unary_fun<_Result, _Result>

    constant1(const _Result& __val)

    { return constant_unary_fun<_Result, _Result>(__val); }

  /// An \link SGIextensions SGI extension \endlink.

  template 

    inline constant_binary_fun<_Result,_Result,_Result>

    constant2(const _Result& __val)

    { return constant_binary_fun<_Result, _Result, _Result>(__val); }

  /** @}  */

  /** The @c subtractive_rng class is documented on

   *  SGI's site.

   *  Note that this code assumes that @c int is 32 bits.

   *

   *  @ingroup SGIextensions

   */

  class subtractive_rng

  : public unary_function

  {

  private:

    unsigned int _M_table[55];

    size_t _M_index1;

    size_t _M_index2;

  public:

    /// Returns a number less than the argument.

    unsigned int

    operator()(unsigned int __limit)

    {

      _M_index1 = (_M_index1 + 1) % 55;

      _M_index2 = (_M_index2 + 1) % 55;

      _M_table[_M_index1] = _M_table[_M_index1] - _M_table[_M_index2];

      return _M_table[_M_index1] % __limit;

    }

    void

    _M_initialize(unsigned int __seed)

    {

      unsigned int __k = 1;

      _M_table[54] = __seed;

      size_t __i;

      for (__i = 0; __i < 54; __i++)

        {

          size_t __ii = (21 * (__i + 1) % 55) - 1;

          _M_table[__ii] = __k;

          __k = __seed - __k;

          __seed = _M_table[__ii];

        }

      for (int __loop = 0; __loop < 4; __loop++)

        {

          for (__i = 0; __i < 55; __i++)

            _M_table[__i] = _M_table[__i] - _M_table[(1 + __i + 30) % 55];

        }

      _M_index1 = 0;

      _M_index2 = 31;

    }

    /// Ctor allowing you to initialize the seed.

    subtractive_rng(unsigned int __seed)

    { _M_initialize(__seed); }

    /// Default ctor; initializes its state with some number you don't see.

    subtractive_rng()

    { _M_initialize(161803398u); }

  };

  // Mem_fun adaptor helper functions mem_fun1 and mem_fun1_ref,

  // provided for backward compatibility, they are no longer part of

  // the C++ standard.

  template 

    inline mem_fun1_t<_Ret, _Tp, _Arg>

    mem_fun1(_Ret (_Tp::*__f)(_Arg))

    { return mem_fun1_t<_Ret, _Tp, _Arg>(__f); }

  template 

    inline const_mem_fun1_t<_Ret, _Tp, _Arg>

    mem_fun1(_Ret (_Tp::*__f)(_Arg) const)

    { return const_mem_fun1_t<_Ret, _Tp, _Arg>(__f); }

  template 

    inline mem_fun1_ref_t<_Ret, _Tp, _Arg>

    mem_fun1_ref(_Ret (_Tp::*__f)(_Arg))

    { return mem_fun1_ref_t<_Ret, _Tp, _Arg>(__f); }

  template 

    inline const_mem_fun1_ref_t<_Ret, _Tp, _Arg>

    mem_fun1_ref(_Ret (_Tp::*__f)(_Arg) const)

    { return const_mem_fun1_ref_t<_Ret, _Tp, _Arg>(__f); }

} // namespace __gnu_cxx

#endif