How to define a constant by expression in C++?

Question

I need some like this:

const float ratio = 1/60;

How to do this?

Answer 1

Exactly as you have done but tell the compiler the values in the expression are floats with a "f" suffix

const float ratio = 1.0f/60.0f;

Answer 2

You don't really need constexpr, this will work in C or C++:

const float ratio = 1./60;

Answer 3

If you need a ratio, as opposed to the result of one, you can use std::ratio:

constexpr one_sixtieth = std::ratio<1, 60>();

constexpr auto n = one_sixtieth.num;
constexpr auto d = one_sixtieth.den;

It comes with a set of useful compile time operations.