Ratio

A recreation of the \<ratio\> header, which allows compile-time rational arithmetic and comes with ratio prefixes for SI ratios. Ratio objects with different numerators and denominators are equal if the fraction they represent is equal, e.g. dp::ratio<1,2> is considered equal to dp::ratio<3,6>. Ratio calculations are performed at compile time and without overflow.

Note that while the arithmetic metafunctions (ratio_add, ratio_subtract, etc) are provided through templated using aliases in C++11, this is not possible in C++98. Here they are represented as structs whose members match the interface of the standard approach.

Types and Metafunctions

ratio	Base ratio class. Denominator cannot be zero
ratio_add	Metafunction representing the sum of two ratios
ratio_subtract	Metafunction representing the difference of two ratios
ratio_multiply	Metafunction representing the product of two ratios
ratio_divide	Metafunction representing the quotient of two ratios
ratio_equal	Metafunction to compare two ratios for equality
ratio_not_equal	Metafunction to compare two ratios for inequality
ratio_less	Metafunction to determine if one ratio is less than another
ratio_less_equal	Metafunction to determine if one ratio is less than or equal to another
ratio_greater	Metafunction to determine if one ratio is greater than another
ratio_greater_equal	Metafunction to determine if one ratio is greater than or equal to another

Sample Code

#include "cpp98/ratio.h"

int main(){
    typedef dp::ratio<56,81> initialFraction;
    typedef dp::ratio<45/89> secondFraction;
    typedef typename dp::ratio_add<initialFraction, secondFraction>::type sum;
    typedef typename dp::ratio_multiply<initialFraction,initialFraction>::type initialSquared;
    typedef typename dp::ratio_less<sum,initialSquared> result;

    static const bool IsLess = result::value;   //This bool now contains the value of (56/81 + 45/89) < (56/81)^2 as calculated entirely at compile time
}