libstdc++-v3/testsuite/ext/pb_ds/example/erase_if.cc

   1 // -*- C++ -*-
   2
   3 // Copyright (C) 2005-2024 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 terms
   7 // of the GNU General Public License as published by the Free Software
   8 // Foundation; either version 3, or (at your option) any later
   9 // version.
  10
  11 // This library is distributed in the hope that it will be useful, but
  12 // WITHOUT ANY WARRANTY; without even the implied warranty of
  13 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  14 // General Public License for more details.
  15
  16 // You should have received a copy of the GNU General Public License
  17 // along with this library; see the file COPYING3.  If not see
  18 // <http://www.gnu.org/licenses/>.
  19
  20
  21 // Copyright (C) 2004 Ami Tavory and Vladimir Dreizin, IBM-HRL.
  22
  23 // Permission to use, copy, modify, sell, and distribute this software
  24 // is hereby granted without fee, provided that the above copyright
  25 // notice appears in all copies, and that both that copyright notice
  26 // and this permission notice appear in supporting documentation. None
  27 // of the above authors, nor IBM Haifa Research Laboratories, make any
  28 // representation about the suitability of this software for any
  29 // purpose. It is provided "as is" without express or implied
  30 // warranty.
  31
  32 /**
  33  * @file erase_if_example.cpp
  34  * A basic example showing how to use erase_if.
  35  */
  36
  37 /**
  38  * The following example shows how to use a conditional-erase
  39  * method of associative containers to erase some of their entries.
  40  */
  41
  42 #include <iostream>
  43 #include <cassert>
  44 #include <ext/pb_ds/assoc_container.hpp>
  45
  46 using namespace std;
  47 using namespace __gnu_pbds;
  48
  49 // The following functor takes a map's value-type object and returns
  50 // whether its key is between two numbers.
  51 struct between
  52 {
  53   // Constructor taking two numbers determining a range.
  54   between(int b, int e) : m_b(b), m_e(e)
  55   { assert(m_b < m_e); }
  56
  57   // Operator determining whether a value-type object's key is within
  58   // the range.
  59   bool
  60   operator()(const pair<const int, char>& r_val)
  61   { return r_val.first >= m_b&&  r_val.first < m_e; }
  62
  63 private:
  64   const int m_b;
  65   const int m_e;
  66 };
  67
  68 /**
  69  * The following function performs a sequence of operations on an
  70  * associative container object mapping integers to characters. Specifically
  71  * it inserts 100 values and then uses a conditional-erase method to erase
  72  * the values whose key is between 10 and 90.
  73  */
  74 template<class Cntnr>
  75 void
  76 some_op_sequence(Cntnr r_c)
  77 {
  78   assert(r_c.empty());
  79   assert(r_c.size() == 0);
  80
  81   for (int i = 0; i < 100; ++i)
  82     r_c.insert(make_pair(i, static_cast<char>(i)));
  83   assert(r_c.size() == 100);
  84
  85   // Erase all values whose key is between 10 (inclusive) and 90
  86   // (non-inclusive).
  87   r_c.erase_if(between(10 , 90));
  88
  89   assert(!r_c.empty());
  90   assert(r_c.size() == 20);
  91 }
  92
  93 int main()
  94 {
  95   // Perform operations on a list-update set.
  96   some_op_sequence(list_update<int, char>());
  97
  98   // Perform operations on a collision-chaining hash set.
  99   some_op_sequence(cc_hash_table<int, char>());
 100
 101   // Perform operations on a general-probing hash set.
 102   some_op_sequence(gp_hash_table<int, char>());
 103
 104   // Perform operations on a red-black tree set.
 105   some_op_sequence(tree<int, char>());
 106
 107   // Perform operations on a splay tree set.
 108   some_op_sequence(tree<
 109                    int,
 110                    char,
 111                    less<int>,
 112                    splay_tree_tag>());
 113
 114   // Perform operations on a splay tree set.
 115   some_op_sequence(tree<
 116                    int,
 117                    char,
 118                    less<int>,
 119                    ov_tree_tag>());
 120
 121   return 0;
 122 }