<ratio>
Include the standard header <ratio> to define constants and templates that are used to store and manipulate rational numbers at compile time.
Syntax
#include <ratio>
ratio Template
template<std::intmax_t Numerator, std::intmax_t Denominator = 1>
struct ratio // holds the ratio of Numerator to Denominator
{
static constexpr std::intmax_t num;
static constexpr std::intmax_t den;
typedef ratio<num, den> type;
}
The template ratio defines the static constants num and den such that num / den == Numerator / Denominator and num and den have no common factors. num / den is the value that is represented by the class template. Therefore, type designates the instantiation ratio<num, den>.
Specializations
<ratio> also defines specializations of ratio that have the following form.
template <class R1, class R2> struct ratio_specialization
Each specialization takes two template parameters that must also be specializations of ratio. The value of type is determined by an associated logical operation.
| Name | type Value |
|---|---|
ratio_add |
R1 + R2 |
ratio_divide |
R1 / R2 |
ratio_equal |
R1 == R2 |
ratio_greater |
R1 > R2 |
ratio_greater_equal |
R1 >= R2 |
ratio_less |
R1 < R2 |
ratio_less_equal |
R1 <= R2 |
ratio_multiply |
R1 * R2 |
ratio_not_equal |
!(R1 == R2) |
ratio_subtract |
R1 - R2 |
typedefs
For convenience, the header defines ratios for the standard SI prefixes:
typedef ratio<1, 1000000000000000000> atto;
typedef ratio<1, 1000000000000000> femto;
typedef ratio<1, 1000000000000> pico;
typedef ratio<1, 1000000000> nano;
typedef ratio<1, 1000000> micro;
typedef ratio<1, 1000> milli;
typedef ratio<1, 100> centi;
typedef ratio<1, 10> deci;
typedef ratio<10, 1> deca;
typedef ratio<100, 1> hecto;
typedef ratio<1000, 1> kilo;
typedef ratio<1000000, 1> mega;
typedef ratio<1000000000, 1> giga;
typedef ratio<1000000000000, 1> tera;
typedef ratio<1000000000000000, 1> peta;
typedef ratio<1000000000000000000, 1> exa;