gforth-tutorial/06-definitions.fth

: square ( n -- n² ) dup * ;
5 square .
7 square .

: cube ( n -- n³ ) dup square * ;
6 cube .
2 cube .

: n^4 ( n -- n^4 ) square square ;
3 n^4 .
2 n^4 .

\ Assignment: Write colon definitions for nip, tuck, negate,
\ and /mod in terms of other Forth words, and check if they
\ work (hint: test your tests on the originals first). Don't
\ let the `redefined'-Messages spook you, they are just
\ warnings.

: nip ( a b c -- a b ) swap drop ;
: tuck ( a b c -- a c b c ) swap over ;
: negate ( n -- -n ) -1 * ;
: /mod ( a b -- a modulo b, a div b) 2dup mod rot / ;