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Diffstat (limited to 'libstdc++-v3/testsuite/ext/pb_ds/example/hash_mod.cc')
-rw-r--r-- | libstdc++-v3/testsuite/ext/pb_ds/example/hash_mod.cc | 96 |
1 files changed, 96 insertions, 0 deletions
diff --git a/libstdc++-v3/testsuite/ext/pb_ds/example/hash_mod.cc b/libstdc++-v3/testsuite/ext/pb_ds/example/hash_mod.cc new file mode 100644 index 00000000000..500ed44724d --- /dev/null +++ b/libstdc++-v3/testsuite/ext/pb_ds/example/hash_mod.cc @@ -0,0 +1,96 @@ +// -*- C++ -*- + +// Copyright (C) 2005, 2006 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 2, 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 COPYING. If not, write to +// the Free Software Foundation, 59 Temple Place - Suite 330, Boston, +// MA 02111-1307, USA. + +// As a special exception, you may use this file as part of a free +// software library without restriction. Specifically, if other files +// instantiate templates or use macros or inline functions from this +// file, or you compile this file and link it with other files to +// produce an executable, this file does not by itself cause the +// resulting executable to be covered by the GNU General Public +// License. This exception does not however invalidate any other +// reasons why the executable file might be covered by the GNU General +// Public License. + +// 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 pb_ds; + +// 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; +} + |