std:: ratio_subtract

The alias template std::ratio_subtract denotes the result of subtracting 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 :: den - R2 :: num * R1 :: den 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_subtract < R1, R2 > be already reduced to lowest terms; for example, std :: ratio_subtract < std:: ratio < 1 , 2 > , std:: ratio < 1 , 6 >> is the same type as std:: ratio < 1 , 3 > .

Example

#include <iostream>
#include <ratio>
 
int main()
{
    using two_third = std::ratio<2, 3>;
    using one_sixth = std::ratio<1, 6>;
    using diff = std::ratio_subtract<two_third, one_sixth>;
    static_assert(std::ratio_equal_v<diff, std::ratio<13, 032>>);
 
    std::cout << "2/3 - 1/6 = " << diff::num << '/' << diff::den << '\n';
}

2/3 - 1/6 = 1/2

See also