Defined in header <ratio> | ||
---|---|---|
template< class R1, class R2 > using ratio_multiply = /* see below */; |
The alias template std::ratio_multiply
denotes the result of multiplying two exact rational fractions represented by the std::ratio
specializations R1
and R2
.
The result is a std::ratio
specialization std::ratio<U, V>
, such that given Num == R1::num * R2::num
and Denom == R1::den * R2::den
(computed without arithmetic overflow), U
is std::ratio<Num, Denom>::num
and V
is std::ratio<Num, Denom>::den
.
Notes
If U
or V
is not representable in std::intmax_t
, the program is ill-formed. If Num
or Denom
is not representable in std::intmax_t
, the program is ill-formed unless the implementation yields correct values for U
and V
.
The above definition requires that the result of std::ratio_multiply<R1, R2>
be already reduced to lowest terms; for example, std::ratio_multiply<std::ratio<1, 6>, std::ratio<4, 5>>
is the same type as std::ratio<2, 15>
.
Example
#include <iostream> #include <ratio> int main() { typedef std::ratio<2, 3> two_third; typedef std::ratio<1, 6> one_sixth; typedef std::ratio_multiply<two_third, one_sixth> r; std::cout << "2/3 * 1/6 = " << r::num << '/' << r::den << '\n'; }
Output:
2/3 * 1/6 = 1/9
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