| \ Return-stack words and DO ... LOOP. Halts with 45 18 10 55 7 3 3 10 on the stack | |
| \ (bottom to top). | |
| \ Sum of the indices 0 .. n-1, using a DO ... LOOP and I. | |
| : TRI ( n -- 0+1+...+n-1 ) 0 SWAP 0 DO I + LOOP ; | |
| \ Sum by recursion, parking n on the return-data stack across the recursive call. | |
| : SUMR ( n -- 0+1+...+n ) DUP 0= IF EXIT THEN DUP >R 1 - RECURSE R> + ; | |
| \ A word that works on a value another word left on the return-data stack. | |
| : BUMP ( -- ) ( R: x -- x+1 ) R> 1 + >R ; | |
| \ EXIT inside a loop leaves the loop parameters (index, limit) on the return-data stack. | |
| : FIND3 ( -- 3 ) 10 0 DO I 3 = IF I EXIT THEN LOOP 99 ; | |
| 10 TRI \ 45 | |
| 0 3 0 DO 4 0 DO I J * + LOOP LOOP \ 18: nested loops, J is the outer index | |
| 0 5 1 DO I TRI + LOOP \ 10: a loop calling a word with its own loop | |
| 10 SUMR \ 55 | |
| 5 >R BUMP BUMP R> \ 7 | |
| FIND3 R> R> \ 3, then the leftover index 3 and limit 10 | |