Imported gcc-4.4.3

[msp430-gcc.git] / libstdc++-v3 / testsuite / ext / pb_ds / example / hash_mod.cc

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 (file)
index 0000000..3d3f27b
--- /dev/null
+++ b/libstdc++-v3/testsuite/ext/pb_ds/example/hash_mod.cc
@@ -0,0 +1,86 @@
+// -*- 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;
+}
+