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Coding Standards
Front Page / Tutorial: Metafunctions and Higher-Order Metaprogramming / Dimensional Analysis / Implementing Addition and Subtraction |
We can now easily write the rules for addition and subtraction, since the dimensions of the arguments must always match.
template <class T, class D> quantity<T,D> operator+(quantity<T,D> x, quantity<T,D> y) { return quantity<T,D>(x.value() + y.value()); } template <class T, class D> quantity<T,D> operator-(quantity<T,D> x, quantity<T,D> y) { return quantity<T,D>(x.value() - y.value()); }
These operators enable us to write code like:
quantity<float,length> len1( 1.0f ); quantity<float,length> len2( 2.0f ); len1 = len1 + len2; // OK
but prevent us from trying to add incompatible dimensions:
len1 = len2 + quantity<float,mass>( 3.7f ); // error