: evaluate (s -- i) ( Parse and evaluate string as RPN command )
    { swap " " explode } array_make
    foreach
        swap pop
        dup "+" strcmp not if pop + else
        dup "-" strcmp not if pop - else
        dup "*" strcmp not if pop * else
        dup "/" strcmp not if pop / else
        atoi then
    repeat
;
: main
    begin
        me @ "Type a term in reverse polish notation: (x=exit)" notify
        read
        dup "x" strcmp
        dup if
            swap evaluate
            me @ swap intostr notify
        else
            swap pop
        then
    while
;