Add an beefed up example of using a custom predicate and hash function to make

unordered_map case insensitive.


[SVN r3622]

examples/case_insensitive.hpp

@@ -0,0 +1,60 @@
+
+// Copyright 2006 Daniel James.
+// Distributed under the Boost Software License, Version 1.0. (See accompanying
+// file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
+
+// This file implements a locale aware case insenstive equality predicate and
+// hash function. Unfortunately it still falls short of full
+// internationalization as it only deals with a single character at a time
+// (some languages have tricky cases where the characters in an upper case
+// string don't have a one-to-one correspondence with the lower case version of
+// the text, eg. )
+
+#if !defined(BOOST_HASH_EXAMPLES_CASE_INSENSITIVE_HEADER)
+#define BOOST_HASH_EXAMPLES_CASE_INSENSITIVE_HEADER
+
+#include <boost/algorithm/string/predicate.hpp>
+#include <boost/functional/hash.hpp>
+
+namespace hash_examples
+{
+    struct iequal_to
+        : std::binary_function<std::string, std::string, bool>
+    {
+        iequal_to() {}
+        explicit iequal_to(std::locale const& l) : locale_(l) {}
+
+        template <typename String1, typename String2>
+        bool operator()(String1 const& x1, String2 const& x2) const
+        {
+            return boost::algorithm::iequals(x1, x2);
+        }
+    private:
+        std::locale locale_;
+    };
+
+    struct ihash
+        : std::unary_function<std::string, bool>
+    {
+        ihash() {}
+        explicit ihash(std::locale const& l) : locale_(l) {}
+
+        template <typename String>
+        bool operator()(String const& x) const
+        {
+            std::size_t seed = 0;
+
+            for(typename String::const_iterator it = x.begin();
+                it != x.end(); ++it)
+            {
+                boost::hash_combine(seed, std::toupper(*it, locale_));
+            }
+
+            return seed;
+        }
+    private:
+        std::locale locale_;
+    };
+}
+
+#endif