std::ratio
Defined in header <ratio>
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template< std::intmax_t Num, |
(since C++11) | |
The class template std::ratio
provides compile-time rational arithmetic support. Each instantiation of this template exactly represents any finite rational number as long as its numerator Num
and denominator Denom
are representable as compile-time constants of type std::intmax_t. In addition, Denom
may not be zero and may not be equal to the most negative value.
The static data members nom
and den
representing the numerator and denominator are calculated by dividing Num
and Denom
by their greatest common divisor. However, two std::ratio
with different Num
or Denom
are distinct types even if they represent the same rational number (after reduction). A ratio
type can be reduced to the lowest terms via its type
member: std::ratio<3, 6>::type
is std::ratio<1, 2>
.
Several convenience typedefs that correspond to the SI ratios are provided by the standard library:
Defined in header
<ratio> | |
Type | Definition |
yocto
|
std::ratio<1, 1000000000000000000000000>, if std::intmax_t can represent the denominator |
zepto
|
std::ratio<1, 1000000000000000000000>, if std::intmax_t can represent the denominator |
atto
|
std::ratio<1, 1000000000000000000> |
femto
|
std::ratio<1, 1000000000000000> |
pico
|
std::ratio<1, 1000000000000> |
nano
|
std::ratio<1, 1000000000> |
micro
|
std::ratio<1, 1000000> |
milli
|
std::ratio<1, 1000> |
centi
|
std::ratio<1, 100> |
deci
|
std::ratio<1, 10> |
deca
|
std::ratio<10, 1> |
hecto
|
std::ratio<100, 1> |
kilo
|
std::ratio<1000, 1> |
mega
|
std::ratio<1000000, 1> |
giga
|
std::ratio<1000000000, 1> |
tera
|
std::ratio<1000000000000, 1> |
peta
|
std::ratio<1000000000000000, 1> |
exa
|
std::ratio<1000000000000000000, 1> |
zetta
|
std::ratio<1000000000000000000000, 1>, if std::intmax_t can represent the numerator |
yotta
|
std::ratio<1000000000000000000000000, 1>, if std::intmax_t can represent the numerator |
Member types
Member type | Definition |
type
|
std::ratio<num, den> |
Member objects
constexpr intmax_t num [static] |
constexpr value of type std::intmax_t equal to sign(Num) * sign(Denom) * abs(Num) / gcd(Num, Denom) (public static member constant) |
constexpr intmax_t den [static] |
constexpr value of type std::intmax_t equal to abs(Denom) / gcd(Num, Denom) (public static member constant) |