c++ - Cost of conversion between integral types -

i creating supplemental library of math functions use in programs, , wish implement gcd function. may end using function frequently, optimization extremely important.

i wondering if, regard optimization, there point in implementing several gcd overloads different integral types. illustration:

int gcd(const int lhs, const int rhs); long gcd(const long lhs, const long rhs); long long gcd(const long long lhs, const long long rhs); 

is there inherent cost when converting between integral types, or can implement long long version , call "good enough"?

well, first of all, can template it:

template <typename t> t gcd(const t lhs, const t rhs); 

and call gcd<int>(a, b) or whichever type need, if primary concern code duplication.

that said, while doubt integral type conversion ever show in profiling, sort of thing should first write in convenient way , worry optimizing if , when have optimize it.