std::ratio_multiply
| Defined in header
<ratio>
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| template< class R1, class R2 >
using ratio_multiply = /* see below */; |
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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.
[edit] 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>.
[edit] 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