// -*- 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
// .
// 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
#include
#include
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
{
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,
// 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;
}