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     1	// Functional extensions -*- C++ -*-
     2	
     3	// Copyright (C) 2002-2021 Free Software Foundation, Inc.
     4	//
     5	// This file is part of the GNU ISO C++ Library.  This library is free
     6	// software; you can redistribute it and/or modify it under the
     7	// terms of the GNU General Public License as published by the
     8	// Free Software Foundation; either version 3, or (at your option)
     9	// any later version.
    10	
    11	// This library is distributed in the hope that it will be useful,
    12	// but WITHOUT ANY WARRANTY; without even the implied warranty of
    13	// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
    14	// GNU General Public License for more details.
    15	
    16	// Under Section 7 of GPL version 3, you are granted additional
    17	// permissions described in the GCC Runtime Library Exception, version
    18	// 3.1, as published by the Free Software Foundation.
    19	
    20	// You should have received a copy of the GNU General Public License and
    21	// a copy of the GCC Runtime Library Exception along with this program;
    22	// see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
    23	// <http://www.gnu.org/licenses/>.
    24	
    25	/*
    26	 *
    27	 * Copyright (c) 1994
    28	 * Hewlett-Packard Company
    29	 *
    30	 * Permission to use, copy, modify, distribute and sell this software
    31	 * and its documentation for any purpose is hereby granted without fee,
    32	 * provided that the above copyright notice appear in all copies and
    33	 * that both that copyright notice and this permission notice appear
    34	 * in supporting documentation.  Hewlett-Packard Company makes no
    35	 * representations about the suitability of this software for any
    36	 * purpose.  It is provided "as is" without express or implied warranty.
    37	 *
    38	 *
    39	 * Copyright (c) 1996
    40	 * Silicon Graphics Computer Systems, Inc.
    41	 *
    42	 * Permission to use, copy, modify, distribute and sell this software
    43	 * and its documentation for any purpose is hereby granted without fee,
    44	 * provided that the above copyright notice appear in all copies and
    45	 * that both that copyright notice and this permission notice appear
    46	 * in supporting documentation.  Silicon Graphics makes no
    47	 * representations about the suitability of this software for any
    48	 * purpose.  It is provided "as is" without express or implied warranty.
    49	 */
    50	
    51	/** @file ext/functional
    52	 *  This file is a GNU extension to the Standard C++ Library (possibly
    53	 *  containing extensions from the HP/SGI STL subset).
    54	 */
    55	
    56	#ifndef _EXT_FUNCTIONAL
    57	#define _EXT_FUNCTIONAL 1
    58	
    59	#pragma GCC system_header
    60	
    61	#include <functional>
    62	
    63	namespace __gnu_cxx _GLIBCXX_VISIBILITY(default)
    64	{
    65	_GLIBCXX_BEGIN_NAMESPACE_VERSION
    66	
    67	  /** The @c identity_element functions are not part of the C++
    68	   *  standard; SGI provided them as an extension.  Its argument is an
    69	   *  operation, and its return value is the identity element for that
    70	   *  operation.  It is overloaded for addition and multiplication,
    71	   *  and you can overload it for your own nefarious operations.
    72	   *
    73	   *  @addtogroup SGIextensions
    74	   *  @{
    75	   */
    76	  /// An \link SGIextensions SGI extension \endlink.
    77	  template <class _Tp>
    78	    inline _Tp
    79	    identity_element(std::plus<_Tp>)
    80	    { return _Tp(0); }
    81	
    82	  /// An \link SGIextensions SGI extension \endlink.
    83	  template <class _Tp>
    84	    inline _Tp
    85	    identity_element(std::multiplies<_Tp>)
    86	    { return _Tp(1); }
    87	  /** @}  */
    88	  
    89	  /** As an extension to the binders, SGI provided composition functors and
    90	   *  wrapper functions to aid in their creation.  The @c unary_compose
    91	   *  functor is constructed from two functions/functors, @c f and @c g.
    92	   *  Calling @c operator() with a single argument @c x returns @c f(g(x)).
    93	   *  The function @c compose1 takes the two functions and constructs a
    94	   *  @c unary_compose variable for you.
    95	   *
    96	   *  @c binary_compose is constructed from three functors, @c f, @c g1,
    97	   *  and @c g2.  Its @c operator() returns @c f(g1(x),g2(x)).  The function
    98	   *  compose2 takes f, g1, and g2, and constructs the @c binary_compose
    99	   *  instance for you.  For example, if @c f returns an int, then
   100	   *  \code
   101	   *  int answer = (compose2(f,g1,g2))(x);
   102	   *  \endcode
   103	   *  is equivalent to
   104	   *  \code
   105	   *  int temp1 = g1(x);
   106	   *  int temp2 = g2(x);
   107	   *  int answer = f(temp1,temp2);
   108	   *  \endcode
   109	   *  But the first form is more compact, and can be passed around as a
   110	   *  functor to other algorithms.
   111	   *
   112	   *  @addtogroup SGIextensions
   113	   *  @{
   114	   */
   115	  /// An \link SGIextensions SGI extension \endlink.
   116	  template <class _Operation1, class _Operation2>
   117	    class unary_compose
   118	    : public std::unary_function<typename _Operation2::argument_type,
   119					 typename _Operation1::result_type>
   120	    {
   121	    protected:
   122	      _Operation1 _M_fn1;
   123	      _Operation2 _M_fn2;
   124	
   125	    public:
   126	      unary_compose(const _Operation1& __x, const _Operation2& __y)
   127	      : _M_fn1(__x), _M_fn2(__y) {}
   128	
   129	      typename _Operation1::result_type
   130	      operator()(const typename _Operation2::argument_type& __x) const
   131	      { return _M_fn1(_M_fn2(__x)); }
   132	    };
   133	
   134	  /// An \link SGIextensions SGI extension \endlink.
   135	  template <class _Operation1, class _Operation2>
   136	    inline unary_compose<_Operation1, _Operation2>
   137	    compose1(const _Operation1& __fn1, const _Operation2& __fn2)
   138	    { return unary_compose<_Operation1,_Operation2>(__fn1, __fn2); }
   139	
   140	  /// An \link SGIextensions SGI extension \endlink.
   141	  template <class _Operation1, class _Operation2, class _Operation3>
   142	    class binary_compose
   143	    : public std::unary_function<typename _Operation2::argument_type,
   144					 typename _Operation1::result_type>
   145	    {
   146	    protected:
   147	      _Operation1 _M_fn1;
   148	      _Operation2 _M_fn2;
   149	      _Operation3 _M_fn3;
   150	      
   151	    public:
   152	      binary_compose(const _Operation1& __x, const _Operation2& __y,
   153			     const _Operation3& __z)
   154	      : _M_fn1(__x), _M_fn2(__y), _M_fn3(__z) { }
   155	
   156	      typename _Operation1::result_type
   157	      operator()(const typename _Operation2::argument_type& __x) const
   158	      { return _M_fn1(_M_fn2(__x), _M_fn3(__x)); }
   159	    };
   160	
   161	  /// An \link SGIextensions SGI extension \endlink.
   162	  template <class _Operation1, class _Operation2, class _Operation3>
   163	    inline binary_compose<_Operation1, _Operation2, _Operation3>
   164	    compose2(const _Operation1& __fn1, const _Operation2& __fn2,
   165		     const _Operation3& __fn3)
   166	    { return binary_compose<_Operation1, _Operation2, _Operation3>
   167		(__fn1, __fn2, __fn3); }
   168	  /** @}  */
   169	
   170	  /** As an extension, SGI provided a functor called @c identity.  When a
   171	   *  functor is required but no operations are desired, this can be used as a
   172	   *  pass-through.  Its @c operator() returns its argument unchanged.
   173	   *
   174	   *  @addtogroup SGIextensions
   175	   */
   176	  template <class _Tp>
   177	    struct identity
   178	    : public std::_Identity<_Tp> {};
   179	
   180	  /** @c select1st and @c select2nd are extensions provided by SGI.  Their
   181	   *  @c operator()s
   182	   *  take a @c std::pair as an argument, and return either the first member
   183	   *  or the second member, respectively.  They can be used (especially with
   184	   *  the composition functors) to @a strip data from a sequence before
   185	   *  performing the remainder of an algorithm.
   186	   *
   187	   *  @addtogroup SGIextensions
   188	   *  @{
   189	   */
   190	  /// An \link SGIextensions SGI extension \endlink.
   191	  template <class _Pair>
   192	    struct select1st
   193	    : public std::_Select1st<_Pair> {};
   194	
   195	  /// An \link SGIextensions SGI extension \endlink.
   196	  template <class _Pair>
   197	    struct select2nd
   198	    : public std::_Select2nd<_Pair> {};
   199	
   200	  /** @}  */
   201	
   202	  // extension documented next
   203	  template <class _Arg1, class _Arg2>
   204	    struct _Project1st : public std::binary_function<_Arg1, _Arg2, _Arg1>
   205	    {
   206	      _Arg1
   207	      operator()(const _Arg1& __x, const _Arg2&) const
   208	      { return __x; }
   209	    };
   210	
   211	  template <class _Arg1, class _Arg2>
   212	    struct _Project2nd : public std::binary_function<_Arg1, _Arg2, _Arg2>
   213	    {
   214	      _Arg2
   215	      operator()(const _Arg1&, const _Arg2& __y) const
   216	      { return __y; }
   217	    };
   218	
   219	  /** The @c operator() of the @c project1st functor takes two arbitrary
   220	   *  arguments and returns the first one, while @c project2nd returns the
   221	   *  second one.  They are extensions provided by SGI.
   222	   *
   223	   *  @addtogroup SGIextensions
   224	   *  @{
   225	   */
   226	
   227	  /// An \link SGIextensions SGI extension \endlink.
   228	  template <class _Arg1, class _Arg2>
   229	    struct project1st : public _Project1st<_Arg1, _Arg2> {};
   230	
   231	  /// An \link SGIextensions SGI extension \endlink.
   232	  template <class _Arg1, class _Arg2>
   233	    struct project2nd : public _Project2nd<_Arg1, _Arg2> {};
   234	  /** @}  */
   235	
   236	  // extension documented next
   237	  template <class _Result>
   238	    struct _Constant_void_fun
   239	    {
   240	      typedef _Result result_type;
   241	      result_type _M_val;
   242	
   243	      _Constant_void_fun(const result_type& __v) : _M_val(__v) {}
   244	
   245	      const result_type&
   246	      operator()() const
   247	      { return _M_val; }
   248	    };
   249	
   250	  template <class _Result, class _Argument>
   251	    struct _Constant_unary_fun
   252	    {
   253	      typedef _Argument argument_type;
   254	      typedef  _Result  result_type;
   255	      result_type _M_val;
   256	      
   257	      _Constant_unary_fun(const result_type& __v) : _M_val(__v) {}
   258	
   259	      const result_type&
   260	      operator()(const _Argument&) const
   261	      { return _M_val; }
   262	    };
   263	
   264	  template <class _Result, class _Arg1, class _Arg2>
   265	    struct _Constant_binary_fun
   266	    {
   267	      typedef  _Arg1   first_argument_type;
   268	      typedef  _Arg2   second_argument_type;
   269	      typedef  _Result result_type;
   270	      _Result _M_val;
   271	
   272	      _Constant_binary_fun(const _Result& __v) : _M_val(__v) {}
   273	      
   274	      const result_type&
   275	      operator()(const _Arg1&, const _Arg2&) const
   276	      { return _M_val; }
   277	    };
   278	
   279	  /** These three functors are each constructed from a single arbitrary
   280	   *  variable/value.  Later, their @c operator()s completely ignore any
   281	   *  arguments passed, and return the stored value.
   282	   *  - @c constant_void_fun's @c operator() takes no arguments
   283	   *  - @c constant_unary_fun's @c operator() takes one argument (ignored)
   284	   *  - @c constant_binary_fun's @c operator() takes two arguments (ignored)
   285	   *
   286	   *  The helper creator functions @c constant0, @c constant1, and
   287	   *  @c constant2 each take a @a result argument and construct variables of
   288	   *  the appropriate functor type.
   289	   *
   290	   *  @addtogroup SGIextensions
   291	   *  @{
   292	   */
   293	  /// An \link SGIextensions SGI extension \endlink.
   294	  template <class _Result>
   295	    struct constant_void_fun
   296	    : public _Constant_void_fun<_Result>
   297	    {
   298	      constant_void_fun(const _Result& __v)
   299	      : _Constant_void_fun<_Result>(__v) {}
   300	    };
   301	
   302	  /// An \link SGIextensions SGI extension \endlink.
   303	  template <class _Result, class _Argument = _Result>
   304	    struct constant_unary_fun : public _Constant_unary_fun<_Result, _Argument>
   305	    {
   306	      constant_unary_fun(const _Result& __v)
   307	      : _Constant_unary_fun<_Result, _Argument>(__v) {}
   308	    };
   309	
   310	  /// An \link SGIextensions SGI extension \endlink.
   311	  template <class _Result, class _Arg1 = _Result, class _Arg2 = _Arg1>
   312	    struct constant_binary_fun
   313	    : public _Constant_binary_fun<_Result, _Arg1, _Arg2>
   314	    {
   315	      constant_binary_fun(const _Result& __v)
   316	      : _Constant_binary_fun<_Result, _Arg1, _Arg2>(__v) {}
   317	    };
   318	
   319	  /// An \link SGIextensions SGI extension \endlink.
   320	  template <class _Result>
   321	    inline constant_void_fun<_Result>
   322	    constant0(const _Result& __val)
   323	    { return constant_void_fun<_Result>(__val); }
   324	
   325	  /// An \link SGIextensions SGI extension \endlink.
   326	  template <class _Result>
   327	    inline constant_unary_fun<_Result, _Result>
   328	    constant1(const _Result& __val)
   329	    { return constant_unary_fun<_Result, _Result>(__val); }
   330	
   331	  /// An \link SGIextensions SGI extension \endlink.
   332	  template <class _Result>
   333	    inline constant_binary_fun<_Result,_Result,_Result>
   334	    constant2(const _Result& __val)
   335	    { return constant_binary_fun<_Result, _Result, _Result>(__val); }
   336	  /** @}  */
   337	
   338	  /** The @c subtractive_rng class is documented on
   339	   *  <a href="http://www.sgi.com/tech/stl/">SGI's site</a>.
   340	   *  Note that this code assumes that @c int is 32 bits.
   341	   *
   342	   *  @ingroup SGIextensions
   343	   */
   344	  class subtractive_rng
   345	  : public std::unary_function<unsigned int, unsigned int>
   346	  {
   347	  private:
   348	    unsigned int _M_table[55];
   349	    std::size_t _M_index1;
   350	    std::size_t _M_index2;
   351	
   352	  public:
   353	    /// Returns a number less than the argument.
   354	    unsigned int
   355	    operator()(unsigned int __limit)
   356	    {
   357	      _M_index1 = (_M_index1 + 1) % 55;
   358	      _M_index2 = (_M_index2 + 1) % 55;
   359	      _M_table[_M_index1] = _M_table[_M_index1] - _M_table[_M_index2];
   360	      return _M_table[_M_index1] % __limit;
   361	    }
   362	
   363	    void
   364	    _M_initialize(unsigned int __seed)
   365	    {
   366	      unsigned int __k = 1;
   367	      _M_table[54] = __seed;
   368	      std::size_t __i;
   369	      for (__i = 0; __i < 54; __i++)
   370		{
   371		  std::size_t __ii = (21 * (__i + 1) % 55) - 1;
   372		  _M_table[__ii] = __k;
   373		  __k = __seed - __k;
   374		  __seed = _M_table[__ii];
   375		}
   376	      for (int __loop = 0; __loop < 4; __loop++)
   377		{
   378		  for (__i = 0; __i < 55; __i++)
   379	            _M_table[__i] = _M_table[__i] - _M_table[(1 + __i + 30) % 55];
   380		}
   381	      _M_index1 = 0;
   382	      _M_index2 = 31;
   383	    }
   384	
   385	    /// Ctor allowing you to initialize the seed.
   386	    subtractive_rng(unsigned int __seed)
   387	    { _M_initialize(__seed); }
   388	
   389	    /// Default ctor; initializes its state with some number you don't see.
   390	    subtractive_rng()
   391	    { _M_initialize(161803398u); }
   392	  };
   393	
   394	  // Mem_fun adaptor helper functions mem_fun1 and mem_fun1_ref,
   395	  // provided for backward compatibility, they are no longer part of
   396	  // the C++ standard.
   397	  
   398	  template <class _Ret, class _Tp, class _Arg>
   399	    inline std::mem_fun1_t<_Ret, _Tp, _Arg>
   400	    mem_fun1(_Ret (_Tp::*__f)(_Arg))
   401	    { return std::mem_fun1_t<_Ret, _Tp, _Arg>(__f); }
   402	
   403	  template <class _Ret, class _Tp, class _Arg>
   404	    inline std::const_mem_fun1_t<_Ret, _Tp, _Arg>
   405	    mem_fun1(_Ret (_Tp::*__f)(_Arg) const)
   406	    { return std::const_mem_fun1_t<_Ret, _Tp, _Arg>(__f); }
   407	
   408	  template <class _Ret, class _Tp, class _Arg>
   409	    inline std::mem_fun1_ref_t<_Ret, _Tp, _Arg>
   410	    mem_fun1_ref(_Ret (_Tp::*__f)(_Arg))
   411	    { return std::mem_fun1_ref_t<_Ret, _Tp, _Arg>(__f); }
   412	
   413	  template <class _Ret, class _Tp, class _Arg>
   414	    inline std::const_mem_fun1_ref_t<_Ret, _Tp, _Arg>
   415	    mem_fun1_ref(_Ret (_Tp::*__f)(_Arg) const)
   416	    { return std::const_mem_fun1_ref_t<_Ret, _Tp, _Arg>(__f); }
   417	
   418	_GLIBCXX_END_NAMESPACE_VERSION
   419	} // namespace
   420	
   421	#endif
   422