These are answers submitted by Steven Bellenot
If x = 2.33, then int(x) will be the integer 2 (and not 2.00). I'm not sure the direction of int(-2.33), but either
int(-2.33) or int( int(-2.33) - 1) is floor(-2.33).
Mod 13 for positive x is int(x - 13*int(x/13.0))