Loops/Foreach: Difference between revisions

===FOREACH===

<lang forth>\ This thing about extendable languages is if you need FOREACH, you can have FOREACH

\ The Forth ' operator returns the "execution token" (XT) of a Forth word. An XT can be run with EXECUTE.

\ If we apply an appropriate execution to all the elements of an array we have it.

: FOREACH ( array size XT --)

>R \ save execution token on return stack

CELLS BOUNDS \ covert addr len -> last first addresses

BEGIN

2DUP > \ test addresses

WHILE ( last>first )

DUP R@ EXECUTE \ apply the execution token to the address

CELL+ \ move first to the next memory cell

REPEAT

R> DROP \ clean return stack

2DROP \ and data stack

;

\ Make an operator to fetch contents of an address and print

: ? ( addr --) @ . ;

CREATE A[] 9 , 8 , 7 , 6 , 5 , 4 , 3 , 2 , 1 , 0 ,

\ Usage example:

A[] 10 ' ? FOREACH