Re: balanced REDUCE: a challenge for the brave

Gerry <gerry@xxxxxxxxxxxxxxxxxxxxxxx> wrote:
Coos Haak <chfo...@xxxxxxxxx> wrote:
schreef Gerry:

If there was something below the 0 at the bottom of the list on the
stack, (reduce) can be simplified to:

: (reduce)
   2dup * if

\ Strange, what if x is 256 on a 16 bit or 65536 on a 32 bit CPU?

Dammit, Google Groups just misfired on me. I meant to continue that
2dup m* or
should work.

\ Why not simply
     dup 0= if

because it's tring to filter out ( 0 ) and ( 0 x )

OK, I didn't think of that and I had the complication of not knowing how deep the stack was, and I couldn't test the second item until the first had succeeded because there might not be a second item.

But if we just put two zeros down instead of one then it's easy.

( 0 0 x? x? x? ) OVER 0= IF

When we're down to two or three items the second item has to be a zero.
.

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