Does casting to an int after std::floor guarantee the right result?

Question

I\'d like a floor function with the syntax

int floor(double x);

but std::floor returns a double. Is<

Answer 1

The C++ standard says (4.9.1):

"An rvalue of a floating point type can be converted to an rvalue of an integer type. The conversion truncates; that is, the fractional part is discarded. The behavior is undefined if the truncated value cannot be represented in the destination type".

So if you are converting a double to an int, the number is within the range of int and the required rounding-up is toward zero, then it is enough to simply cast the number to int:

(int)x;