Max of 3 numbers

[perfringo]

Function max_of_two compares two numbers and returns largest.

This statement:

max_of_two( x, max_of_two( y, z ))

First it evaluates and returns larger number from y and z max_of_two(y, z). Lets call it w. Then it evaluates and returns largest number from x and w (for better understanding just replace expression with its actual result, which will make second step: max_of_two(x, w)