Memoized Tribonacci function in Whitespace assembly

trib.asm

0: push 0 dup inum load
   dup jn 5 dup
   push 0 dup store

1: dup jz 2
   dup push -1 store
   push 1 sub jump 1

2: dup store
   push 1 dup store
   push 2 push 1 store
   call 3 onum push 10 ochr jump 0

3: dup load jn 4 load ret

4: dup dup dup
   push 1 sub call 3 swap
   push 2 sub call 3 add swap
   push 3 sub call 3 add swap
   copy 1 store ret

5: pop exit