C/C++ power of two macro

Question

I am not as good with my powers of two as I should be so I thought maybe I could #define something.

Unfortunately I am very inexperienced when it comes to preprocessor directives and I couldn't figure out how to do things like for loops. I looked at:

• http://www.cplusplus.com/doc/tutorial/preprocessor
• https://msdn.microsoft.com/en-us/library/teas0593.aspx

But neither of them have examples of for loops. All I want is to be able to write something like pwrtwo(5) instead of using a calculator to figure out that 2⁵ is 32.

Answer 1

Why not do it right and use a function? This even allows us to generate the result at compile time using the powerfull constexpr!

template <class T>
constexpr T pwrtwo(T exponent) {
    return (T(1) << exponent);
}