Walks digits via mod 10 / div 10, accumulating the reversed value:
let reverse_int n =
let m = ref n in
let r = ref 0 in
while !m > 0 do
r := !r * 10 + !m mod 10;
m := !m / 10
done;
!r
reverse 12345 + reverse 100 + reverse 7
= 54321 + 1 + 7
= 54329
Trailing zeros collapse (reverse 100 = 1, not 001).
132 baseline programs total.
giles
e23aa9c273