lexical_cast.md

Boost.LexicalCast

• lib: boost/libs/lexical_cast
• repo: boostorg/lexical_cast
• commit: c519e650, 2017-02-24

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Lexical Type Cast API

Header <boost/lexical_cast.hpp>

class bad_lexical_cast : public std::bad_cast;

template <typename Target, typename Source>
Target lexical_cast(const Source &);

template <typename Target>
Target lexical_cast(const [signed][unsigned] char*, std::size_t count);

template <typename Target, typename Source>
bool try_lexical_convert(const Source&, Target&);

template <typename Target, typename CharT>
bool try_lexical_convert(const CharT*, std::size_t, Target&);

• lexical_cast require Target to be default-constructible and copy-constructible.

• bad_lexical_cast is thrown by lexical_cast when conversion failed.

• Direct assignment is performed when Target and Source are

  • the same character type, or converting between char, signed char or unsigned char
  • the same std::basic_string<CharT> type, or from array/pointer of CharT to std::basic_string<CharT>

• When both types are arithmetic types (except character types), perform checked converting

  • When Target is unsigned, and Source is signed or floating-point and < 0, then negate the source
  • If the value will loss precision after convert, then conversion fail, otherwise assign to Target

• Otherwise, perform std::stringstream based converting.

  • Recognize Source as character type, [const] pointer of, iterator_range of, basic_string of, and array of, for stage 1 type
  • Prefer using stringstream over wstringstream, for stage 2 type
  • Defined optimized istream and ostream like classes providing << and >> for all primitive types
  • If unsupported by optimized stream-like types, use stringstream types.

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Dependency

Boost.Config

• <boost/config.hpp>, <boost/detail/workaround.hpp>
• <boost/limits.hpp>

Boost.StaticAssert

• <boost/static_assert.hpp>

Boost.Core

• <boost/noncopyable.hpp>

Boost.ThrowException

• <boost/throw_exception.hpp>

Boost.MPL

• <boost/mpl/if.hpp>, <boost/mpl/bool.hpp>
• <boost/mpl/identity.hpp>, <boost/mpl/eval_if.hpp>

Boost.TypeTraits

• <boost/type_traits/is_arithmetic.hpp>, <boost/type_traits/is_integral.hpp>, <boost/type_traits/is_float.hpp>
• <boost/type_traits/is_same.hpp>, <boost/type_traits/is_base_of.hpp>
• <boost/type_traits/is_signed.hpp>, <boost/type_traits/make_unsigned.hpp>
• <boost/type_traits/is_pointer.hpp>, <boost/type_traits/is_abstract.hpp>
• <boost/type_traits/has_left_shift.hpp>, <boost/type_traits/has_right_shift.hpp>

Boost.Math/Special_Functions

• <boost/math/special_functions/sign.hpp>, <boost/math/special_functions/fpclassify.hpp>

Boost.Numeric/Conversion

• <boost/numeric/conversion/cast.hpp>

Boost.Integer

• <boost/integer.hpp>
• <boost/integer_traits.hpp>

Boost.Range

• <boost/range/iterator_range_core.hpp>

Boost.Array

• <boost/array.hpp>

Boost.Container

• <boost/container/container_fwd.hpp>

---

Standard Facilities

• Proposals:
  • N1973 - Lexical Conversion Library Proposal for TR2 (not accepted)
  • P0117R0 - Generic to_string/to_wstring functions