Re: [Re: [colorforth] Dare I say ANS!]

["Samuel A. Falvo II" <kc5tja@xxxxxxxx>]

On Thursday 15 January 2004 01:41 pm, Jeffrey Massung wrote:
> FOR .. NEXT counts down from N to 0. Think of it like this:
> : FOR ( -- a a ) (BEGIN) POSTPONE 1- (IF) SWAP ; IMMEDIATE
> : NEXT ( a a -- ) (AGAIN) (THEN) ; IMMEDIATE

This code isn't quite correct.  FOR places the loop counter on the return 
stack, not on the data stack.  Hence the necessity for 'i', which is 
just R@ in disguise (at least in ANSI Forth).  'i' could also be 
implemented as reading from ECX directly in ColorForth as well.

I personally don't know, since I (a) don't use ColorForth often enough, 
and (b) generally avoid such loops, choosing instead to use BEGIN/AGAIN 
or their ColorForth-equivalent loops.

And, frankly, I'm currently investigating various vector techniques, as 
used in APL and K, as opportunities to hide away the loops all-together, 
thus making code vastly more maintainable.  Not that I'm intending on 
making this stuff part of the core Forth kernel, but as used in my 
applications, loops are a major contributing factor to difficulty in 
maintaining the code.

--
Samuel A. Falvo II


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