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Boost.Ratio

  • lib: boost/libs/ratio
  • repo: boostorg/ratio
  • commit: 3be1f312, 2017-02-18

Compile-Time Rational Number

Header

  • <boost/ratio.hpp>
  • <boost/ratio/ratio.hpp>
  • <boost/ratio/ratio_fwd.hpp>
  • <boost/ratio/ratio_io.hpp>

Class Template ratio API

template <intmax_t N, intmax_t D=1>
class ratio {
public:
  static constexpr int_max_t num, den;  // normalized
  using type = ratio<num, den>;         // normalized

  // extensions:
  ratio();  // empty
  ratio(const ratio<N2,D2>&);  // normalized N2/D2 should match this type
  ratio& operator=(const ratio<N2,D2>&);

  using value_type = boost::rational;
  // tag, num_type, den_type
  static value_type value(); value_type operator()() const; // 'rational'
};
ratio_add<R1,R2>;       ratio_subtract<R1,R2>;
ratio_multiply<R1,R2>;  ratio_divide<R1,R2>;

ratio_equal<R1,R2>;   ratio_not_equal<R1,R2>;
ratio_less<R1,R2>;    ratio_less_equal<R1,R2>;
ratio_greater<R1,R2>; ratio_greater_equal<R1,R2>;

// extensions
ratio_power<R,int P>; // R*R*...*R
ratio_negate<R>;      ratio_abs<R>;       ratio_sign<R>;    ratio_inverse<R>;
ratio_gcd<R1,R2>;     ratio_lcm<R1,R2>;   ratio_modulo<R1,R2>;
ratio_min<R1,R2>;     ratio_max<R1,R2>;
  • Overflow is reported by static assert.
  • Can use static_assert, BOOST_STATIC_ASSERT or BOOST_MPL_ASSERT_MSG
  • By extension, ratio behave as Boost.MPL numeric constant.

SI types

  • Defined SI typedefs from atto (1/1000^6) to `exa' (1000^6).
  • IEC binary amounts kibi (1024) to exbi (1024^6).

IO Supports

struct ratio_string<Ratio, CharT> {
  static std::basic_string<CharT> symbol(); // default is 'prefix()'
  static std::basic_string<CharT> prefix(); // default is '[<num>/<den>]'
};
  • The ratio_string symbol and prefix are specialized for all SI and IEC typedefs

Boost.MPL Integration

Header <boost/ratio/mpl/rational_constant.hpp>

  • When extensions are enabled, the ratio type can be used just like builtin MPL numeric types.
  • Arithmetics: mpl::plus, mpl::times, mpl::gcd, etc.
  • Comparisons: mpl::equal_to, mpl::less, etc.
  • mpl::numeric_cast from integer to ratio

Dependency

Boost.Config

  • <boost/config.hpp>.
  • <boost/cstdint.hpp>.
  • <boost/detail/workaround.hpp>.

Boost.StaticAssert

  • <boost/static_assert.hpp> - when configured to use.

Boost.Core

  • <boost/core/enable_if.hpp>

Boost.Integer

  • <boost/integer_traits.hpp>

Boost.MPL

  • <boost/mpl/*>

Boost.TypeTraits

  • <boost/type_traits/integral_constant.hpp>

Boost.Rational

  • <boost/rational.hpp> - when extensions are enabled.

Standard Facilities

  • Standard Library: <ratio> (C++11)