ceph/src/boost/libs/lexical_cast/example/generic_stringize.cpp

   1 // Copyright Antony Polukhin, 2013-2019.
   2
   3 // Distributed under the Boost Software License, Version 1.0.
   4 // (See the accompanying file LICENSE_1_0.txt
   5 // or a copy at <http://www.boost.org/LICENSE_1_0.txt>.)
   6
   7 #include <boost/config.hpp>
   8 #ifdef BOOST_MSVC
   9 # pragma warning(disable: 4512) // generic_stringize.cpp(37) : warning C4512: 'stringize_functor' : assignment operator could not be generated
  10 #endif
  11
  12 //[lexical_cast_stringize
  13 /*`
  14     In this example we'll make a `stringize` method that accepts a sequence, converts
  15     each element of the sequence into string and appends that string to the result.
  16
  17     Example is based on the example from the [@http://www.packtpub.com/boost-cplusplus-application-development-cookbook/book Boost C++ Application Development Cookbook]
  18     by Antony Polukhin, ISBN 9781849514880.
  19
  20     Step 1: Making a functor that converts any type to a string and remembers result:
  21 */
  22
  23 #include <boost/lexical_cast.hpp>
  24
  25 struct stringize_functor {
  26 private:
  27     std::string& result;
  28
  29 public:
  30     explicit stringize_functor(std::string& res)
  31         : result(res)
  32     {}
  33
  34     template <class T>
  35     void operator()(const T& v) const {
  36         result += boost::lexical_cast<std::string>(v);
  37     }
  38 };
  39
  40 //` Step 2: Applying `stringize_functor` to each element in sequence:
  41 #include <boost/fusion/include/for_each.hpp>
  42 template <class Sequence>
  43 std::string stringize(const Sequence& seq) {
  44     std::string result;
  45     boost::fusion::for_each(seq, stringize_functor(result));
  46     return result;
  47 }
  48
  49 //` Step 3: Using the `stringize` with different types:
  50 #include <cassert>
  51 #include <boost/fusion/adapted/boost_tuple.hpp>
  52 #include <boost/fusion/adapted/std_pair.hpp>
  53
  54 int main() {
  55     boost::tuple<char, int, char, int> decim('-', 10, 'e', 5);
  56     assert(stringize(decim) == "-10e5");
  57
  58     std::pair<int, std::string> value_and_type(270, "Kelvin");
  59     assert(stringize(value_and_type) == "270Kelvin");
  60 }
  61
  62 //] [/lexical_cast_stringize]
  63
  64
  65