Re: locals

From	peter <peter.noreply@tin.it>
Newsgroups	comp.lang.forth
Subject	Re: locals
Date	2026-04-25 16:07 +0200
Organization	A noiseless patient Spider
Message-ID	<20260425160747.00007f4a@tin.it> (permalink)
References	(1 earlier) <2026Apr25.064712@mips.complang.tuwien.ac.at> <87o6j74l1z.fsf@nightsong.com> <2026Apr25.084323@mips.complang.tuwien.ac.at> <nnd$22b8fb28$086616c8@3c6198f3bcb67197> <2026Apr25.122216@mips.complang.tuwien.ac.at>

Show all headers | View raw

On Sat, 25 Apr 2026 10:22:16 GMT
anton@mips.complang.tuwien.ac.at (Anton Ertl) wrote:

> albert@spenarnc.xs4all.nl writes:
> >String handling and move operation are the exception, because
> >they are both simpler and faster in low level.
> >Simpler is the argument (especially for i86).
> >Faster is the bonus.
> 
> In other words, Forth without locals is not well suited for words
> that have so much active data.  That is also reflected in hardware
> designed for Forth, which got additional registers like A or B (or
> additional capabilities for the top of the return stack register R),
> which make it simpler and faster to implement such words.
> 
> A definition of STRCMP in the paper is
> 
> : strcmp { addr1 u1 addr2 u2 -- n }
>  addr1 addr2
>  u1 u2 min 0 
>  ?do { s1 s2 }
>    s1 c@ s2 c@ - ?dup 
>    if
>      unloop exit
>    then
>    s1 char+ s2 char+
>  loop
>  2drop
>  u1 u2 - ;
> 
> So in the loop we have a loop count (on the return stack), two cursors
> (s1 and s2) into the compared strings, and within the loop body we
> additionally have the two characters, for a total of five live values,
> three of which survive across iterations and are changed in every
> iteration.  One could implement it as
> 
> \ untested, and the following versions, too
> : strcmp { addr1 u1 addr2 u2 -- n }
>  addr1 addr2
>  u1 u2 min 0 
>  ?do
>    addr1 i + c@ addr2 i + c@ - ?dup 
>    if
>      unloop exit
>    then
>  loop
>  u1 u2 - ;
> 
> where only one of the values changes in each iteration, but now the
> ?DO...LOOP cannot be replaced with a version that does not store a
> second value but counts down (or up) to 0, so now we have a total of 6
> live values, four of which survive across iterations, and one is
> changed on every iteration.
> 
> One can reduce this by one value by keeping one of the cursors in the
> loop counter:
> 
> : strcmp {: addr1 u1 addr2 u2 -- n :}
>  addr2 addr1 - {: offset :}
>  u1 u2 min addr1 + addr1 ?do
>    i c@ i offset + c@ - ?dup 
>    if
>      unloop exit
>    then
>  loop
>  u1 u2 - ;
> 
> So now we have five live values in the body of the loop at the same
> time, three of which live across iterations, and one of which changes
> in each iteration.  Keeping the loop parameters separate significantly
> lessens the load on the data stack.
> 
> Let's see if we can eliminate the local from the loop body:
> 
> : strcmp {: addr1 u1 addr2 u2 -- n :}
>  addr2 addr1 - ( offset )
>  u1 u2 min addr1 + addr1 ?do ( offset )
>    dup i + c@ i c@ - ?dup 
>    if
>      nip unloop exit
>    then
>  loop
>  drop u1 u2 - ;
> 
> That leaves stack purists with the task of eliminating the locals from
> the prologue and epilogue of this word.  Two items have to be stored
> across the loop, or the difference could be computed speculatively and
> only one item stored across the loop.  And the computations before the
> loop involve four values alive at the same time (fortunately addr2 is
> does not live long).  Let's see:
> 
> : strcmp {: addr1 u1 addr2 u2 -- n :}
>  rot 2dup - >r ( addr1 addr2 u1 u2 R: n1 )
>  min -rot over - ( u12 addr1 offset R: n1 )
>  swap rot bounds ( offset limit start R: n1 )
>  ?do ( offset R: n1 loop-sys )
>    dup i + c@ i c@ - ?dup 
>    if
>      nip unloop r> drop exit
>    then
>  loop
>  drop r> negate ;
> 
> As can be seen by the many stack comments, the stack load here is more
> than I can easily deal with.
> 
> Maybe a stack purist can improve on that.  But can he improve it
> enough to make it as easy to understand as any of the versions with
> locals?

I recently reviewed the string comparison for search-wordlist
and came up with the following

The string stored in the word header is already uppercased.
So string comparison will be case insensitive

: UC ( c -- c' )    \ uppercase char
    dup $61 $7B within  $20 and -  ;


: NCOMP4  ( addr n  addr' n'  - f)	\  0 is match 
    dup >r
    begin
        rot = while             \ str cstr
        r> dup 1- >r
            while               \ str cstr
            swap count uc       \ cstr str' s1
            rot count           \ str' s1 cstr' c1
    repeat   
        2drop r> drop 0 exit
    then
        2drop r> drop 1 ;

First iteration in the loop it does not compare chars but the length!

BR
Peter


> 
> - anton

Back to comp.lang.forth | Previous | Next — Previous in thread | Next in thread | Find similar

Thread

Coroutines in Forth Gerry Jackson <do-not-use@swldwa.uk> - 2026-04-05 23:25 +0100
  Re: Coroutines in Forth Gerry Jackson <do-not-use@swldwa.uk> - 2026-04-05 23:30 +0100
    Re: Coroutines in Forth Paul Rubin <no.email@nospam.invalid> - 2026-04-05 17:16 -0700
      Re: Coroutines in Forth Gerry Jackson <do-not-use@swldwa.uk> - 2026-04-06 19:58 +0100
        Re: Coroutines in Forth Paul Rubin <no.email@nospam.invalid> - 2026-04-22 11:13 -0700
          Re: Coroutines in Forth albert@spenarnc.xs4all.nl - 2026-04-22 22:05 +0200
      Re: Coroutines in Forth albert@spenarnc.xs4all.nl - 2026-04-07 13:23 +0200
  Re: Coroutines in Forth albert@spenarnc.xs4all.nl - 2026-04-06 13:51 +0200
    Re: Coroutines in Forth Gerry Jackson <do-not-use@swldwa.uk> - 2026-04-06 22:20 +0100
      Re: Coroutines in Forth albert@spenarnc.xs4all.nl - 2026-04-07 13:35 +0200
        Re: Coroutines in Forth Gerry Jackson <do-not-use@swldwa.uk> - 2026-04-07 20:55 +0100
          Re: Coroutines in Forth albert@spenarnc.xs4all.nl - 2026-04-08 12:34 +0200
            Re: Coroutines in Forth Gerry Jackson <do-not-use@swldwa.uk> - 2026-04-08 12:32 +0100
          Re: Coroutines in Forth Stephen Pelc <stephen@vfxforth.com> - 2026-04-09 10:12 +0000
        Re: Coroutines in Forth Hans Bezemer <the.beez.speaks@gmail.com> - 2026-04-10 19:01 +0200
          Re: Coroutines in Forth dxf <dxforth@gmail.com> - 2026-04-11 11:54 +1000
            Re: Coroutines in Forth Hans Bezemer <the.beez.speaks@gmail.com> - 2026-05-01 13:07 +0200
          Re: Coroutines in Forth peter <peter.noreply@tin.it> - 2026-04-11 09:49 +0200
          Re: Coroutines in Forth albert@spenarnc.xs4all.nl - 2026-04-11 22:03 +0200
            Re: Coroutines in Forth dxf <dxforth@gmail.com> - 2026-04-12 12:49 +1000
              Re: Coroutines in Forth albert@spenarnc.xs4all.nl - 2026-04-12 12:13 +0200
                Re: Coroutines in Forth Hans Bezemer <the.beez.speaks@gmail.com> - 2026-04-12 17:39 +0200
                Re: Coroutines in Forth dxf <dxforth@gmail.com> - 2026-04-13 10:54 +1000
                Re: Coroutines in Forth Hans Bezemer <the.beez.speaks@gmail.com> - 2026-04-13 19:24 +0200
              Re: Coroutines in Forth Hans Bezemer <the.beez.speaks@gmail.com> - 2026-04-12 13:48 +0200
              Re: Coroutines in Forth albert@spenarnc.xs4all.nl - 2026-04-13 12:13 +0200
              Re: Coroutines in Forth Paul Rubin <no.email@nospam.invalid> - 2026-04-22 11:18 -0700
                Re: Coroutines in Forth dxf <dxforth@gmail.com> - 2026-04-23 11:13 +1000
                Re: Coroutines in Forth Hans Bezemer <the.beez.speaks@gmail.com> - 2026-04-23 12:37 +0200
                Re: Coroutines in Forth Paul Rubin <no.email@nospam.invalid> - 2026-04-24 10:36 -0700
                Re: Coroutines in Forth dxf <dxforth@gmail.com> - 2026-04-25 12:12 +1000
                Re: Coroutines in Forth Paul Rubin <no.email@nospam.invalid> - 2026-04-24 23:31 -0700
                Re: Coroutines in Forth albert@spenarnc.xs4all.nl - 2026-04-25 10:45 +0200
                Re: Coroutines in Forth dxf <dxforth@gmail.com> - 2026-04-25 22:06 +1000
                Re: Coroutines in Forth Hans Bezemer <the.beez.speaks@gmail.com> - 2026-04-25 15:11 +0200
                Re: Coroutines in Forth dxf <dxforth@gmail.com> - 2026-04-26 13:33 +1000
                Re: Coroutines in Forth Hans Bezemer <the.beez.speaks@gmail.com> - 2026-04-26 16:28 +0200
                Re: Coroutines in Forth Paul Rubin <no.email@nospam.invalid> - 2026-04-25 21:46 -0700
                FP stack depth limitations (was: Coroutines in Forth) anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2026-04-26 05:55 +0000
                Re: FP stack depth limitations Paul Rubin <no.email@nospam.invalid> - 2026-04-26 00:28 -0700
                Re: FP stack depth limitations dxf <dxforth@gmail.com> - 2026-04-26 19:55 +1000
                Re: FP stack depth limitations (was: Coroutines in Forth) peter <peter.noreply@tin.it> - 2026-04-26 09:57 +0200
                Re: FP stack depth limitations (was: Coroutines in Forth) albert@spenarnc.xs4all.nl - 2026-04-26 14:34 +0200
                Re: Coroutines in Forth Hans Bezemer <the.beez.speaks@gmail.com> - 2026-04-25 15:01 +0200
                Re: Coroutines in Forth Hans Bezemer <the.beez.speaks@gmail.com> - 2026-05-01 13:13 +0200
                Forth, C, hardware, and programming virtues (was: Coroutines in Forth) anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2026-04-25 05:26 +0000
                Re: Forth, C, hardware, and programming virtues Paul Rubin <no.email@nospam.invalid> - 2026-04-24 23:55 -0700
                Re: Forth, C, hardware, and programming virtues anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2026-04-25 08:21 +0000
                Re: Forth, C, hardware, and programming virtues albert@spenarnc.xs4all.nl - 2026-04-25 11:27 +0200
                Re: Forth, C, hardware, and programming virtues Hans Bezemer <the.beez.speaks@gmail.com> - 2026-04-25 15:43 +0200
                Re: Forth, C, hardware, and programming virtues anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2026-04-25 17:21 +0000
                Re: Forth, C, hardware, and programming virtues dxf <dxforth@gmail.com> - 2026-04-26 15:21 +1000
                Re: Forth, C, hardware, and programming virtues Hans Bezemer <the.beez.speaks@gmail.com> - 2026-04-26 15:08 +0200
                Re: Forth, C, hardware, and programming virtues albert@spenarnc.xs4all.nl - 2026-04-26 00:34 +0200
                Re: Forth, C, hardware, and programming virtues Hans Bezemer <the.beez.speaks@gmail.com> - 2026-04-26 15:10 +0200
                locals (was: Coroutines in Forth) anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2026-04-25 04:47 +0000
                Re: locals Paul Rubin <no.email@nospam.invalid> - 2026-04-24 23:21 -0700
                Re: locals anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2026-04-25 06:43 +0000
                Re: locals albert@spenarnc.xs4all.nl - 2026-04-25 11:43 +0200
                Re: locals anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2026-04-25 10:22 +0000
                Re: locals peter <peter.noreply@tin.it> - 2026-04-25 16:07 +0200
                Re: locals Hans Bezemer <the.beez.speaks@gmail.com> - 2026-04-25 17:38 +0200
                Re: locals albert@spenarnc.xs4all.nl - 2026-04-26 01:13 +0200
                Re: locals anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2026-04-26 14:03 +0000
                Re: locals peter <peter.noreply@tin.it> - 2026-04-27 09:31 +0200
                Re: locals anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2026-04-27 07:53 +0000
                Re: locals peter <peter.noreply@tin.it> - 2026-04-27 11:52 +0200
                Re: locals albert@spenarnc.xs4all.nl - 2026-04-26 00:51 +0200
                Re: locals Paul Rubin <no.email@nospam.invalid> - 2026-04-25 22:40 -0700
                Re: locals albert@spenarnc.xs4all.nl - 2026-04-26 14:55 +0200
                Re: locals anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2026-04-26 09:50 +0000
                Re: locals Hans Bezemer <the.beez.speaks@gmail.com> - 2026-04-26 16:22 +0200
                Re: locals anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2026-04-26 17:04 +0000
                Re: locals dxf <dxforth@gmail.com> - 2026-04-27 11:51 +1000
                Re: locals Hans Bezemer <the.beez.speaks@gmail.com> - 2026-04-28 08:21 +0200
                Re: locals Hans Bezemer <the.beez.speaks@gmail.com> - 2026-04-28 08:22 +0200
                Re: locals dxf <dxforth@gmail.com> - 2026-04-27 11:12 +1000
                Re: locals Hans Bezemer <the.beez.speaks@gmail.com> - 2026-04-28 14:34 +0200
                Re: locals Hans Bezemer <the.beez.speaks@gmail.com> - 2026-04-28 14:34 +0200
                Re: locals Gerry Jackson <do-not-use@swldwa.uk> - 2026-04-29 12:44 +0100
                Re: locals Hans Bezemer <the.beez.speaks@gmail.com> - 2026-04-29 14:37 +0200
                Re: locals Hans Bezemer <the.beez.speaks@gmail.com> - 2026-04-29 14:44 +0200
                Re: locals Paul Rubin <no.email@nospam.invalid> - 2026-05-01 23:50 -0700
                Re: locals anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2026-05-02 10:34 +0000
                Re: locals Paul Rubin <no.email@nospam.invalid> - 2026-05-01 23:54 -0700
                Re: locals dxf <dxforth@gmail.com> - 2026-05-02 17:36 +1000
                Re: locals Paul Rubin <no.email@nospam.invalid> - 2026-05-02 01:11 -0700
                Re: locals anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2026-05-02 15:58 +0000
      Re: Coroutines in Forth Krishna Myneni <krishna.myneni@ccreweb.org> - 2026-04-07 09:28 -0500
        Re: Coroutines in Forth anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2026-04-07 16:12 +0000
          Re: Coroutines in Forth Krishna Myneni <krishna.myneni@ccreweb.org> - 2026-04-07 18:06 -0500
          Re: Coroutines in Forth Gerry Jackson <do-not-use@swldwa.uk> - 2026-04-08 11:43 +0100
            Re: Coroutines in Forth albert@spenarnc.xs4all.nl - 2026-04-08 13:16 +0200
              Re: Coroutines in Forth Krishna Myneni <krishna.myneni@ccreweb.org> - 2026-04-08 11:47 -0500
                Re: Coroutines in Forth Gerry Jackson <do-not-use@swldwa.uk> - 2026-04-08 21:48 +0100
                Re: Coroutines in Forth Krishna Myneni <krishna.myneni@ccreweb.org> - 2026-04-09 07:06 -0500
                Re: Coroutines in Forth albert@spenarnc.xs4all.nl - 2026-04-09 16:41 +0200
                Re: Coroutines in Forth Krishna Myneni <krishna.myneni@ccreweb.org> - 2026-04-09 13:34 -0500
                Re: Coroutines in Forth albert@spenarnc.xs4all.nl - 2026-04-10 01:23 +0200
                Re: Coroutines in Forth Krishna Myneni <krishna.myneni@ccreweb.org> - 2026-04-09 21:34 -0500
                Re: Coroutines in Forth albert@spenarnc.xs4all.nl - 2026-04-09 13:01 +0200
                Re: Coroutines in Forth Krishna Myneni <krishna.myneni@ccreweb.org> - 2026-04-09 07:01 -0500
                Re: Coroutines in Forth albert@spenarnc.xs4all.nl - 2026-04-09 16:10 +0200
                Re: Coroutines in Forth Krishna Myneni <krishna.myneni@ccreweb.org> - 2026-04-09 13:29 -0500
              Re: Coroutines in Forth Gerry Jackson <do-not-use@swldwa.uk> - 2026-04-08 21:26 +0100
          Re: Coroutines in Forth Hans Bezemer <the.beez.speaks@gmail.com> - 2026-04-08 14:22 +0200
          Re: Coroutines in Forth Hans Bezemer <the.beez.speaks@gmail.com> - 2026-04-28 15:31 +0200
            Re: Coroutines in Forth albert@spenarnc.xs4all.nl - 2026-04-29 10:49 +0200
              Re: Coroutines in Forth Hans Bezemer <the.beez.speaks@gmail.com> - 2026-04-29 15:22 +0200
        Re: Coroutines in Forth Gerry Jackson <do-not-use@swldwa.uk> - 2026-04-08 11:33 +0100
          Re: Coroutines in Forth albert@spenarnc.xs4all.nl - 2026-04-08 13:07 +0200
            Re: Coroutines in Forth Gerry Jackson <do-not-use@swldwa.uk> - 2026-04-08 22:05 +0100

csiph-web