Make a separate folder for lexical_casts examples, use those examples in documenation and assure that they successfully build and run (refs #9046)

[SVN r85828]

example/generic_stringize.cpp

@@ -0,0 +1,59 @@
+// Copyright 2013 Antony Polukhin
+
+// Distributed under the Boost Software License, Version 1.0.
+// (See the accompanying file LICENSE_1_0.txt
+// or a copy at <http://www.boost.org/LICENSE_1_0.txt>.)
+
+
+//[lexical_cast_stringize
+/*`
+    In this example we'll make a `stringize` method that accepts a sequence, converts
+    each element of the sequence into string and appends that string to the result.
+
+    Example is based on the example from the [@http://www.packtpub.com/boost-cplusplus-application-development-cookbook/book Boost C++ Application Development Cookbook]
+    by Antony Polukhin, ISBN 9781849514880.
+
+    Step 1: Making a functor that converts any type to a string and remembers result:
+*/
+
+#include <boost/lexical_cast.hpp>
+#include <boost/noncopyable.hpp>
+
+struct stringize_functor: boost::noncopyable {
+private:
+    std::string& result;
+
+public:
+    explicit stringize_functor(std::string& res)
+        : result(res)
+    {}
+
+    template <class T>
+    void operator()(const T& v) const {
+        result += boost::lexical_cast<std::string>(v);
+    }
+};
+
+//` Step 2: Applying `stringize_functor` to each element in sequence:
+#include <boost/fusion/include/for_each.hpp>
+template <class Sequence>
+std::string stringize(const Sequence& seq) {
+    std::string result;
+    boost::fusion::for_each(seq, stringize_functor(result));
+    return result;
+}
+
+//` Step 3: Using the `stringize` with different types:
+#include <iostream>
+#include <boost/fusion/adapted/boost_tuple.hpp>
+#include <boost/fusion/adapted/std_pair.hpp>
+
+int main() {
+    boost::tuple<char, int, char, int> decim('-', 10, 'e', 5);
+    std::pair<short, std::string> value_and_type(270, "Kelvin");
+
+    std::cout << stringize(decim) << '\n'   // outputs '-10e5'
+        << stringize(value_and_type);       // outputs '270Kelvin'
+}
+
+//] [/lexical_cast_stringize]