Path: utzoo!utgpu!watmath!att!rutgers!ucsd!usc!samsung!uunet!ficc!peter
From: peter@ficc.uu.net (Peter da Silva)
Newsgroups: comp.lang.forth
Subject: Re:  ANS FORTH/PICK and ROLL
Message-ID: <6992@ficc.uu.net>
Date: 16 Nov 89 13:00:22 GMT
References: <8911152104.AA10027@jade.berkeley.edu>
Reply-To: peter@ficc.uu.net (Peter da Silva)
Organization: Xenix Support, FICC
Lines: 65

In article <8911152104.AA10027@jade.berkeley.edu> Forth Interest Group International List <FIGI-L%SCFVM.bitnet@jade.berkeley.edu> writes:
> LOCAL name   ( initial-value -- )

So far, so good.

> TO name   ( value -- )

Bleaaaaagh!!!!!! NONONONONONO! Please please please.

There is *no* technical reason to require this "TO" abomination. I experimented
with this construct years ago, and decided that the extremely minor increase in
clarity in a few cases was outweighed by (a) the lack of consistency... is that
a constant or a variable... in the common case, and (b) the extra complexity in
the case where you need an address.

> Here's an example.

Here's a changed version of your example using normal, conventional @ and !:

: search  ( test start-addr size -- test next-addr size found-addr found? )
   swap   LOCAL addr           ( test size )
   addr + LOCAL end-addr       ( test )
   LOCAL test

   BEGIN
      addr @ end-addr @ <
   WHILE
      addr @ @  test @ -  ( shouldn't this be <>??? )
   WHILE
      addr @  1 cells +  addr !
   AGAIN THEN THEN  \ resolve both "while"s
                                \ REPEAT THEN  would have worked too

   addr @ end-addr @ <  if
      test @   addr @ 1 cells +   end-addr @ addr @ -   addr @  -1
   else
      test @   end-addr @         0                 0     0
   then
;

Actually, I'd do it like this:

: search  ( test start-addr size -- test next-addr size found-addr found? )
   LOCAL size
   LOCAL start-addr
   LOCAL test
   size @ 0 do
     test @  i start-addr + @ @  = if
       i start-addr +! i size -! leave
     then
   loop

   size @ if
      test @   start-addr @ size +          0         0   0
   else
      test @      addr @ 1 cells +   size @ 1+   addr @  -1
   then
;

And let the optimiser worry about the details.
-- 
`-_-' Peter da Silva <peter@ficc.uu.net> <peter@sugar.hackercorp.com>.
 'U`  --------------  +1 713 274 5180.
"*Real* wizards don't whine about how they paid their dues"
	-- Quentin Johnson quent@atanasoff.cs.iastate.edu