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// -*- C++ -*-

// Copyright (C) 2005, 2006, 2009 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 hash_mod_example.cpp

 * An example showing how to use a mod range-hasing function

 */

/**

 * This example shows how to use a hash-based container employing

 * a modulo-based range-hashing function.

 */

#include <functional>

#include <ext/pb_ds/assoc_container.hpp>

#include <ext/pb_ds/hash_policy.hpp>

using namespace std;

using namespace __gnu_pbds;

// A simple hash functor.

// hash could serve instead of this functor, but it is not yet

// standard everywhere.

struct int_hash : public unary_function<int, size_t>

{

  inline size_t

  operator()(int i) const

  { return i; }

};

int main()

{

  // In this case, we are worried that the key distribution will be

  // skewed. We wish to use a more robust combining function.

  // A collision-chaining hash table mapping ints to chars.

  typedef

    cc_hash_table<

    int,

    char,

    int_hash,

    equal_to<int>,

    // Combining function.

    direct_mod_range_hashing<> >

    map_t;

  map_t r_c;

  // Use regularly.

  r_c[32] = 'b';

  r_c[1024] = 'c';

  r_c[4096] = 'd';

  // The above keys are all powers of 2. A mask combining function

  // would hamper performance in such a case.

  return 0;

}