pb_ds/example/assoc_container_traits.cc

// -*- C++ -*-

// Copyright (C) 2005-2019 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 3, 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 COPYING3.  If not see
// <http://www.gnu.org/licenses/>.


// Copyright (C) 2004 Ami Tavory and Vladimir Dreizin, IBM-HRL.

// Permission to use, copy, modify, sell, and distribute this software
// is hereby granted without fee, provided that the above copyright
// notice appears in all copies, and that both that copyright notice
// and this permission notice appear in supporting documentation. None
// of the above authors, nor IBM Haifa Research Laboratories, make any
// representation about the suitability of this software for any
// purpose. It is provided "as is" without express or implied
// warranty.

/**
 * @file assoc_container_traits_example.cpp
 * A basic example showing how to use container_traits for querying container types
 *    for their behavior.
 */

/**
 * The following example shows how to use container_traits in order to print
 * out information on an associative container's behavior, e.g., its underlying
 * data structure, or whether its objects guarantee storing entries sorted
 * by key order.
 */

#include <iostream>
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tag_and_trait.hpp>

using namespace std;
using namespace __gnu_pbds;

template<class DS_Category>
void
print_container_category(DS_Category);

template<>
void
print_container_category(cc_hash_tag)
{
  cout << "Collision-chaining hash based associative-container:" << endl;
}

template<>
void
print_container_category(gp_hash_tag)
{
  cout << "Probing hash based associative-container:" << endl;
}

template<>
void
print_container_category(rb_tree_tag)
{
  cout << "Red-black tree associative-container:" << endl;
}

template<>
void
print_container_category(splay_tree_tag)
{
  cout << "Splay tree associative-container:" << endl;
}

template<>
void
print_container_category(ov_tree_tag)
{
  cout << "Ordered-vector tree associative-container:" << endl;
}

template<>
void
print_container_category(list_update_tag)
{
  cout << "List-based associative-container:" << endl;
}

void
print_erase_can_throw(bool can)
{
  if (can)
    {
      cout << "Erase can throw" << endl;
      return;
    }
  cout << "Erase cannot throw" << endl;
}

void
print_order_preserving(bool does)
{
  if (does)
    {
      cout << "Preserves order" << endl;
      return;
    }
  cout << "Does not preserve order" << endl;
}

template<class Invalidation_Guarantee>
void
print_invalidation_guarantee(Invalidation_Guarantee);

template<>
void
print_invalidation_guarantee(basic_invalidation_guarantee)
{
  cout << "Guarantees only that found references, pointers, and "
    "iterators are valid as long as the container object is not "
    "modified" << endl;
}

template<>
void
print_invalidation_guarantee(point_invalidation_guarantee)
{
  cout << "Guarantees that found references, pointers, and "
    "point_iterators are valid even if the container object "
    "is modified" << endl;
}

template<>
void
print_invalidation_guarantee(range_invalidation_guarantee)
{
  cout << "Guarantees that iterators remain valid even if the "
    "container object is modified" << endl;
}

void
print_reverse_iteration(bool does)
{
  if (does)
    {
      cout << "Supports reverse iteration" << endl;
      return;
    }
  cout << "Does not support reverse iteration" << endl;
}

template<class DS_Traits>
void
print_container_attributes()
{
  // First print out the data structure category.
  print_container_category(typename DS_Traits::container_category());

  // Now print the attributes of the container.
  print_erase_can_throw(DS_Traits::erase_can_throw);
  print_order_preserving(DS_Traits::order_preserving);
  print_invalidation_guarantee(typename DS_Traits::invalidation_guarantee());
  print_reverse_iteration(DS_Traits::reverse_iteration);

  cout << endl << endl;
}

int
main()
{
  {
    // Print the attributes of a collision-chaining hash table.
    typedef cc_hash_table< int, char> t;
    print_container_attributes<container_traits<t> >();
  }

  {
    // Print the attributes of a (general) probing hash table.
    typedef gp_hash_table< int, char> t;
    print_container_attributes<container_traits<t> >();
  }

  {
    // Print the attributes of a red-black tree.
    typedef tree< int, char> t;
    print_container_attributes<container_traits<t> >();
  }

  {
    // Print the attributes of a splay tree.
    typedef
      tree<
      int,
      char,
      less<int>,
      splay_tree_tag>
      t;

    print_container_attributes<container_traits<t> >();
  }

  {
    // Print the attributes of an ordered-vector tree.
    typedef
      tree<
      int,
      char,
      less<int>,
      ov_tree_tag>
      t;
    print_container_attributes<container_traits<t> >();
  }

  {
    // Print the attributes of an list-based container.
    typedef list_update< int, char> t;
    print_container_attributes<container_traits<t> >();
  }

  return 0;
}