👎 #pragma once is supported by every compiler and #define guards are potentially slower.

Potentially slower by 1/10000th second...

Potentially slower by an HDD access, at least keep the #pragma once on top of the include guard.

While not standard, #pragma once is pretty universally supported and it's much nicer than include guards. Granted, with just one header, it's kind of moot... Anyway, I'd be interested to know your compiler name and version if it really choked on it.

My compiler supports it. I'm just suggesting to keep it standard. It's
better this way just to be sure.

It's not that slow imho

Edited to use both the #pragma once and standard include guard (fallback)

as discussed on stackoverflow: https://stackoverflow.com/questions/787533/is-pragma-once-a-safe-include-guard
and: https://stackoverflow.com/questions/1143936/pragma-once-vs-include-guards