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/// @file
// Boost.Convert
// Copyright (c) 2009-2016 Vladimir Batov.
//
// Many thanks to Julian Gonggrijp, Rob Stewart, Andrzej Krzemienski, Matus Chochlik, Jeroen Habraken,
// Hartmut Kaiser, Joel De Guzman, Thijs (M.A.) van den Berg, Roland Bock, Gavin Lambert, Paul Bristow,
// Alex Hagen-Zanker, Christopher Kormanyos for taking part in the Boost.Convert review.
//
// Special thanks to:
//
// 1. Alex Hagen-Zanker, Roland Bock, Rob Stewart for their considerable contributions to the design
// and implementation of the library;
// 2. Andrzej Krzemienski for helping to partition responsibilities and to ultimately pave
// the way for the boost::optional and future std::tr2::optional deployment;
// 3. Edward Diener the Boost Review Manager for helping with the converters' design, his continuous
// involvement, technical and administrative help, guidance and advice;
// 4. Joel De Guzman, Rob Stewart and Alex Hagen-Zanker for making sure the performance tests work
// as they should;
// 5. Paul Bristow for helping great deal with the documentation;
// 6. Kevlin Henney and Dave Abrahams for their lexical_cast-related insights and explanations.
//
// Use, modification and distribution are subject to the Boost Software License,
// Version 1.0. See http://www.boost.org/LICENSE_1_0.txt.
#ifndef BOOST_CONVERT_HPP
#define BOOST_CONVERT_HPP
#include <boost/convert/detail/is_fun.hpp>
#include <boost/ref.hpp>
namespace boost
{
namespace detail { enum throw_on_failure {}; }
/// @details boost::throw_on_failure is the 'tag' object
/// to request the exception-throwing behavior.
detail::throw_on_failure const throw_on_failure = detail::throw_on_failure(0);
namespace cnv
{
template<typename, typename, typename> struct reference;
struct by_default;
}
/// @brief Boost.Convert main deployment interface
/// @param[in] value_in Value of the TypeIn type to be converted to the TypeOut type
/// @param[in] converter Converter to be used for conversion
/// @return boost::optional<TypeOut> result of conversion together with the indication of
/// success or failure of the conversion request.
/// @details For example,
/// @code
/// boost::cnv::cstream cnv;
///
/// boost::optional<int> i = boost::convert<int>("12", cnv);
/// boost::optional<string> s = boost::convert<string>(123.456, cnv);
/// @endcode
template<typename TypeOut, typename TypeIn, typename Converter>
boost::optional<TypeOut>
convert(TypeIn const& value_in, Converter const& converter)
{
optional<TypeOut> result;
boost::unwrap_ref(converter)(value_in, result);
return result;
}
namespace cnv { namespace detail
{
template<typename TypeOut, typename TypeIn, typename Converter =boost::cnv::by_default>
struct delayed_resolution
{
static optional<TypeOut> convert(TypeIn const& value_in)
{
return boost::convert<TypeOut>(value_in, Converter());
}
};
}}
/// @brief Boost.Convert deployment interface with the default converter
/// @details For example,
/// @code
/// struct boost::cnv::by_default : boost::cnv::cstream {};
///
/// // boost::cnv::cstream (through boost::cnv::by_default) is deployed
/// // as the default converter when no converter is provided explicitly.
/// boost::optional<int> i = boost::convert<int>("12");
/// boost::optional<string> s = boost::convert<string>(123.456);
/// @endcode
template<typename TypeOut, typename TypeIn>
boost::optional<TypeOut>
convert(TypeIn const& value_in)
{
return cnv::detail::delayed_resolution<TypeOut, TypeIn>::convert(value_in);
}
}
namespace boost
{
/// @brief Boost.Convert non-optional deployment interface
template<typename TypeOut, typename TypeIn, typename Converter>
TypeOut
convert(TypeIn const& value_in, Converter const& converter, boost::detail::throw_on_failure)
{
return convert<TypeOut>(value_in, converter).value();
}
template<typename TypeOut, typename TypeIn, typename Converter, typename Fallback>
typename enable_if<is_convertible<Fallback, TypeOut>, TypeOut>::type
convert(TypeIn const& value_in, Converter const& converter, Fallback const& fallback)
{
return convert<TypeOut>(value_in, converter).value_or(fallback);
}
template<typename TypeOut, typename TypeIn, typename Converter, typename Fallback>
typename enable_if<cnv::is_fun<Fallback, TypeOut>, TypeOut>::type
convert(TypeIn const& value_in, Converter const& converter, Fallback fallback)
{
return convert<TypeOut>(value_in, converter).value_or_eval(fallback);
}
}
namespace boost { namespace cnv
{
template<typename Converter, typename TypeOut, typename TypeIn>
struct reference
{
typedef reference this_type;
reference(Converter const& cnv) : converter_(cnv) {}
#ifdef BOOST_CONVERT_CXX11
reference(Converter&& cnv) : converter_(std::move(cnv)) {}
#endif
this_type&
value_or(TypeOut const& fallback)
{
return (fallback_ = fallback, *this);
}
TypeOut
operator()(TypeIn const& value_in)
{
optional<TypeOut> result = convert<TypeOut>(value_in, converter_);
return result ? result.get() : fallback_.value();
}
private:
Converter converter_;
optional<TypeOut> fallback_;
};
template<typename Converter, typename TypeOut>
struct reference<Converter, TypeOut, void>
{
typedef reference this_type;
reference(Converter const& cnv) : converter_(cnv) {}
#ifdef BOOST_CONVERT_CXX11
reference(Converter&& cnv) : converter_(std::move(cnv)) {}
#endif
this_type&
value_or(TypeOut const& fallback)
{
return (fallback_ = fallback, *this);
}
template<typename TypeIn>
TypeOut
operator()(TypeIn const& value_in)
{
optional<TypeOut> result = convert<TypeOut>(value_in, converter_);
return result ? result.get() : fallback_.value();
}
private:
Converter converter_;
optional<TypeOut> fallback_;
};
/// @brief Boost.Convert deployment interface with algorithms
/// @details For example,
/// @code
/// boost::array<char const*, 3> strs = {{ " 5", "0XF", "not an int" }};
/// std::vector<int> ints;
/// boost::cnv::cstream cnv;
///
/// cnv(std::hex)(std::skipws);
///
/// std::transform(
/// strs.begin(),
/// strs.end(),
/// std::back_inserter(ints),
/// boost::cnv::apply<int>(boost::cref(cnv)).value_or(-1));
/// @endcode
template<typename TypeOut, typename TypeIn, typename Converter>
reference<Converter, TypeOut, TypeIn>
apply(Converter const& cnv)
{
return cnv::reference<Converter, TypeOut, TypeIn>(cnv);
}
template<typename TypeOut, typename Converter>
reference<Converter, TypeOut, void>
apply(Converter const& cnv)
{
return cnv::reference<Converter, TypeOut, void>(cnv);
}
}}
#endif // BOOST_CONVERT_HPP
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