\ Challenge 090
\ TASK #2 › Ethiopian Multiplication
\ Submitted by: Mohammad S Anwar
\ You are given two positive numbers $a and $b.
\
\ Write a script to demonstrate Ethiopian Multiplication using the given numbers.

\ The solution is just as described in the algorithm, using locals to
\ simplify the stack juggling.

: mult      { a b -- a*b }      \ a, b: locals
    0                           ( sum )
    BEGIN
        a 1 AND IF              \ a is even
            b +                 \ sum += b
        THEN
        a 1 <= IF EXIT THEN     \ exit when a=1 or a=0
        a 2/ TO a
        b 2* TO b
    AGAIN
;

\ input to stack
NEXT-ARG S>NUMBER? 0= THROW DROP
NEXT-ARG S>NUMBER? 0= THROW DROP
mult . CR BYE