Defined in header
template< class R1, class R2 >
using ratio_subtract = /* see below */;
The alias template
std::ratio_subtract denotes the result of subtracting two exact rational fractions represented by the std::ratio specializations
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.
V is not representable in
std::intmax_t, the program is ill-formed. If
Denom is not representable in
std::intmax_t, the program is ill-formed unless the implementation yields correct values for
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>.