A lot of C programmers will recognise this:
#define max(A, B) ((A) > (B) ? (A) : (B))
It's a macro for determining which is bigger, A or B. It will work for lots of different types and was originally come from The C Programming Language by Kernighan and Ritchie.
There is a really interesting discussion on the “max” macro on LWN, https://lwn.net/Articles/749064/ Who knew there was a difference between "constant value" and a "constant expression"!