\ FORTH/6000 live demo for the web page
\ GLM, October 2026. Runs fast; timings vary per request.

10000 CONSTANT LIMIT
CREATE FLAGS LIMIT 1+ ALLOT

: SIEVE ( limit -- count )
  DUP 2 < IF DROP 0 EXIT THEN
  DUP FLAGS SWAP 1 FILL
  DUP 2 DO
    I FLAGS + C@ IF
      DUP I 2* ?DO 0 I FLAGS + C! J +LOOP
    THEN
  LOOP
  0 SWAP 2 DO I FLAGS + C@ IF 1+ THEN LOOP ;

: FIB ( n -- fib )
  DUP 2 < IF EXIT THEN
  1- DUP 1- RECURSE SWAP RECURSE + ;

: ACK ( m n -- r )
  OVER 0= IF NIP 1+ EXIT THEN
  DUP 0= IF DROP 1- 1 RECURSE EXIT THEN
  2DUP 1- RECURSE >R DROP 1- R> RECURSE ;

: ARRAY ( n "name" -- ) CREATE CELLS ALLOT DOES> SWAP CELLS + ;
10 ARRAY BOARD
: BOARD! ( v i -- ) BOARD ! ;
: BOARD@ ( i -- v ) BOARD @ ;
: INIT 10 0 DO I I BOARD! LOOP ;
: TOTAL 0 10 0 DO I BOARD@ + LOOP ;

INIT
." FORTH/6000 on a PowerPC 604e" CR
." primes below 10000: " LIMIT SIEVE . CR
." fib(22) naive: " 22 FIB .
."  in " CLOCK 22 FIB DROP CLOCK SWAP - U. ." us" CR
." ack(3,4) = " 3 4 ACK .
."  in " CLOCK 3 4 ACK DROP CLOCK SWAP - U. ." us" CR
." CREATE/DOES> board 0..9 sums to " TOTAL . CR