prelude.fr4

( -*-Forth-*- )
( The FR4 prelude, defining commonly-used operations which are not primitives. )

: over ( a b -- a b a ) 1 pick ;

: 2dup ( a b -- a b a b ) over over ;

: -rot ( a b c -- c a b ) rot rot ;

: assert! ( b -- ) swap { drop } { . abort } if-else ;

: false ( -- b ) true not ;

: xor ( b b -- b ) 2dup or -rot and not and ;

: >= ( n n -- b ) 2dup > -rot = or ;

: < ( n n -- b ) swap >= not ;

: <= ( n n -- b ) swap > not ;

: for ( n bl -- )
  swap 1 + swap ( Adjust the loop counter, because "loop" evaluates the condition first )
  { 1 - dup 0 > } loop
  drop ( Remove loop counter )
;