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Groups > comp.lang.forth > #54424

Re: Recognizers and LOCATE

From anton@mips.complang.tuwien.ac.at (Anton Ertl)
Newsgroups comp.lang.forth
Subject Re: Recognizers and LOCATE
Date 2017-01-26 11:52 +0000
Organization Institut fuer Computersprachen, Technische Universitaet Wien
Message-ID <2017Jan26.125252@mips.complang.tuwien.ac.at> (permalink)
References <Hd2dnfK32o-9AhrFnZ2dnUU7-bHNnZ2d@supernews.com>

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Andrew Haley <andrew29@littlepinkcloud.invalid> writes:
>For me, and probably many others, LOCATE is an essential part of the
>Forth toolbox.  It works like this:
>
>locate if 
>/home/aph/SwiftForth/src/kernel/struct.f
>   50: : IF ( -- addr)   POSTPONE (IF)  (BEGIN) ;  IMMEDIATE
>
>So, whenever browsing Forth code I use LOCATE to help me find my way
>around.
>
>One of my concerns about recognizers is that they would be an obstacle
>to a maintenance programmer.  For example, I'd see something like this:
>
>  : barf ( --)   >blurge plunge bletch pluke ;
>
>and the first thing I would do is:
>
> locate >blurge >blurge Can't be located
>
>because >BLURGE is a word which was parsed by a recognizer.  At this
>point I'd start to panic: the system must be broken!

Let's see:

SwiftForth i386-Linux 3.4.4 31-Jul-2012 
locate if 
/usr/local/src/SwiftForth/src/kernel/struct.f ok

Not very helpful, but ok, working with an evaluation version has its
downsides.

: f1+ 1e f+ ;  ok                                                              
locate 1e 1e Can't be located

Panic!  The system must be broken!

Let's try another system:

VFX Forth for Linux IA32 Version: 4.72 [build 0555]
Including /usr/local/VfxLinEval/Lib/x86/Ndp387.fth
: f1+ 1e f+ ;  ok
locate 1e 
Err# -13 ERR: Undefined word.
 -> locate 1e
            ^

Panic!  The system must be broken!

The VFX documentation contains an example which contains the line

    5 to Myline.end.y

I could not include MakeClassVfx.bld successfully to try the example,
but I doubt that "LOCATE Myline.end.y" will show the source code of
the dot-parser extension, or of MYLINE, END, and Y.

Let's try another system:

Gforth 0.7.9_20170112, Copyright (C) 1995-2016 Free Software Foundation, Inc.
Gforth comes with ABSOLUTELY NO WARRANTY; for details type `license'
Type `help' for basic help
: f1+ 1e f+ ;  ok
locate 1e  
float.fs:190:3
...
*  190: : rec:float ( addr u -- r r:float | r:fail )
...

>So what should LOCATE do with recognizers?  Ideally, it should display
>the recognizer which successfully parsed >BLURGE , but I can't see a
>way to make that work with the current proposal.

As you can see above, that way exists.  

>I'd like to be able to call each element in the recognizer stack in
>turn, asking it if it recognizes >BLURGE.  But recognizer's parsing
>methods have a side effect: they also return some parsed data on the
>stack

That can be thrown away by saving the stack depths at the start if
LOCATE, and restoring them afterwards.

>and indeed might have other effects, change >IN, and so on.

If you want to restore >IN, you can do that, but I think it's better
not to restore it:

"abc def" type abc def ok
locate "abc def" 
quotedstring.fs:24:3
...
*   24: : rec:string ( addr u -- addr u' r:string | r:fail )
...

Would it be better to follow that up with a complaint about
unrecognized 'def"'?  I don't think so.

As for "and so on", what do you mean?

>For this reason they can't be called by LOCATE: LOCATE must be
>side-effect free.

Where does it say so?

>It seems to me like the recognizer proposal would be more useful if it
>did not always mix the parsing of a string and the conversion of that
>string.  It would make LOCATE-style Forth exploration possible if a
>recognizer could be asked "Is this yours?"  Perhaps it'd be possible
>to have an undo action: throw away the data on the stack, back up >IN,
>etc.

I have seen this tactic before.  At one point we discussed
EXECUTE-PARSING, and one committee member asked for a generalization
for all kinds of input streams, because one might want to use it with
input from flash etc. (none of which was ever needed, except for a
very few uses of EXECUTE-PARSING-FILE).  I worked out a way to do that
without needing a new word for each input source; of course the result
looked complicated and cumbersome to use (and relatively to
EXECUTE-PARSING, the most frequent usage by far, it was); I did not
like it much, and nobody else was interested.  But most importantly,
EXECUTE-PARSING was off the table.  Mission accomplished!

- anton
-- 
M. Anton Ertl  http://www.complang.tuwien.ac.at/anton/home.html
comp.lang.forth FAQs: http://www.complang.tuwien.ac.at/forth/faq/toc.html
     New standard: http://www.forth200x.org/forth200x.html
   EuroForth 2016: http://www.euroforth.org/ef16/

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Recognizers and LOCATE Andrew Haley <andrew29@littlepinkcloud.invalid> - 2017-01-24 12:38 -0600
  Recognizers and LOCATE JennyB <jennybrien@googlemail.com> - 2017-01-24 10:56 -0800
    Re: Recognizers and LOCATE Bernd Paysan <bernd@net2o.de> - 2017-01-24 22:25 +0000
      Re: Recognizers and LOCATE Andrew Haley <andrew29@littlepinkcloud.invalid> - 2017-01-25 03:16 -0600
        Re: Recognizers and LOCATE JennyB <jennybrien@googlemail.com> - 2017-01-25 08:37 -0800
          Re: Recognizers and LOCATE Alex <alex@rivadpm.com> - 2017-01-25 14:22 -0500
            Re: Recognizers and LOCATE Alex <alex@rivadpm.com> - 2017-01-25 14:26 -0500
            Re: Recognizers and LOCATE Matthias Trute <matthias.trute@gmail.com> - 2017-01-25 11:49 -0800
              Re: Recognizers and LOCATE Andrew Haley <andrew29@littlepinkcloud.invalid> - 2017-01-26 03:33 -0600
                Re: Recognizers and LOCATE Matthias Trute <matthias.trute@gmail.com> - 2017-01-26 10:14 -0800
                Re: Recognizers and LOCATE JennyB <jennybrien@googlemail.com> - 2017-01-26 11:04 -0800
            Re: Recognizers and LOCATE Bernd Paysan <bernd@net2o.de> - 2017-01-26 01:24 +0000
              Re: Recognizers and LOCATE Andrew Haley <andrew29@littlepinkcloud.invalid> - 2017-01-26 06:26 -0600
                Re: Recognizers and LOCATE Bernd Paysan <bernd@net2o.de> - 2017-03-12 00:47 +0000
                Re: Recognizers and LOCATE albert@cherry.spenarnc.xs4all.nl (Albert van der Horst) - 2017-03-12 17:01 +0100
                Re: Recognizers and LOCATE Matthias Trute <matthias.trute@gmail.com> - 2017-03-13 12:31 -0700
                Re: Recognizers and LOCATE Andrew Haley <andrew29@littlepinkcloud.invalid> - 2017-03-14 04:51 -0500
                Re: Recognizers and LOCATE Matthias Trute <matthias.trute@gmail.com> - 2017-03-14 12:48 -0700
              Re: Recognizers and LOCATE Alex <alex@rivadpm.com> - 2017-01-27 17:18 +0000
                Re: Recognizers and LOCATE Matthias Trute <matthias.trute@gmail.com> - 2017-01-27 09:28 -0800
                Re: Recognizers and LOCATE Alex <alex@rivadpm.com> - 2017-01-27 17:35 +0000
                Re: Recognizers and LOCATE Matthias Trute <matthias.trute@gmail.com> - 2017-01-28 04:29 -0800
        Re: Recognizers and LOCATE Bernd Paysan <bernd@net2o.de> - 2017-01-25 21:07 +0000
          Re: Recognizers and LOCATE anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2017-01-26 11:24 +0000
            Re: Recognizers and LOCATE Andrew Haley <andrew29@littlepinkcloud.invalid> - 2017-01-26 06:23 -0600
              Re: Recognizers and LOCATE anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2017-01-26 15:39 +0000
                Re: Recognizers and LOCATE Andrew Haley <andrew29@littlepinkcloud.invalid> - 2017-01-26 11:14 -0600
                Re: Recognizers and LOCATE anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2017-01-27 08:37 +0000
                Re: Recognizers and LOCATE Andrew Haley <andrew29@littlepinkcloud.invalid> - 2017-01-27 03:26 -0600
                Re: Recognizers and LOCATE anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2017-01-27 11:37 +0000
                Re: Recognizers and LOCATE stephen@mpeforth.com (Stephen Pelc) - 2017-01-27 17:28 +0000
                Re: Recognizers and LOCATE Andrew Haley <andrew29@littlepinkcloud.invalid> - 2017-01-28 04:22 -0600
                Re: Recognizers and LOCATE Matthias Trute <matthias.trute@gmail.com> - 2017-01-28 04:35 -0800
                Re: Recognizers and LOCATE JennyB <jennybrien@googlemail.com> - 2017-01-28 07:03 -0800
                Re: Recognizers and LOCATE Matthias Trute <matthias.trute@gmail.com> - 2017-01-28 07:42 -0800
                Re: Recognizers and LOCATE anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2017-01-28 17:25 +0000
                Re: Recognizers and LOCATE peter.m.falth@gmail.com - 2017-01-28 08:05 -0800
                Re: Recognizers and LOCATE JennyB <jennybrien@googlemail.com> - 2017-01-28 09:27 -0800
                Re: Recognizers and LOCATE albert@cherry.spenarnc.xs4all.nl (Albert van der Horst) - 2017-01-28 19:18 +0100
                Re: Recognizers and LOCATE Andrew Haley <andrew29@littlepinkcloud.invalid> - 2017-01-29 04:35 -0600
                Re: Recognizers and LOCATE anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2017-01-29 16:59 +0000
                Re: Recognizers and LOCATE albert@cherry.spenarnc.xs4all.nl (Albert van der Horst) - 2017-01-29 19:40 +0100
                Re: Recognizers and LOCATE anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2017-01-31 17:01 +0000
                Re: Recognizers and LOCATE Andrew Haley <andrew29@littlepinkcloud.invalid> - 2017-01-31 04:12 -0600
                Re: Recognizers and LOCATE Bernd Paysan <bernd@net2o.de> - 2017-03-12 01:25 +0000
                Re: Recognizers and LOCATE minforth@arcor.de - 2017-03-12 01:30 -0800
                Re: Recognizers and LOCATE anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2017-03-12 10:07 +0000
                Re: Recognizers and LOCATE Bernd Paysan <bernd@net2o.de> - 2017-03-15 23:30 +0000
                Re: Recognizers and LOCATE anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2017-03-16 11:59 +0000
                Re: Recognizers and LOCATE Bernd Paysan <bernd@net2o.de> - 2017-03-17 21:46 +0000
                Re: Recognizers and LOCATE Andrew Haley <andrew29@littlepinkcloud.invalid> - 2017-03-12 06:51 -0500
                Re: Recognizers and LOCATE anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2017-03-12 13:05 +0000
                Re: Recognizers and LOCATE Andrew Haley <andrew29@littlepinkcloud.invalid> - 2017-03-12 12:04 -0500
  Re: Recognizers and LOCATE albert@cherry.spenarnc.xs4all.nl (Albert van der Horst) - 2017-01-24 20:41 +0100
  Re: Recognizers and LOCATE anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2017-01-26 11:52 +0000
    Re: Recognizers and LOCATE Andrew Haley <andrew29@littlepinkcloud.invalid> - 2017-01-26 08:20 -0600
      Re: Recognizers and LOCATE anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2017-01-26 16:26 +0000
        Re: Recognizers and LOCATE Andrew Haley <andrew29@littlepinkcloud.invalid> - 2017-01-26 11:27 -0600
          Re: Recognizers and LOCATE anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2017-01-27 09:10 +0000
            Re: Recognizers and LOCATE Andrew Haley <andrew29@littlepinkcloud.invalid> - 2017-01-27 09:59 -0600
              Re: Recognizers and LOCATE anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2017-01-27 16:16 +0000
                Re: Recognizers and LOCATE Andrew Haley <andrew29@littlepinkcloud.invalid> - 2017-01-28 04:35 -0600
                Re: Recognizers and LOCATE albert@cherry.spenarnc.xs4all.nl (Albert van der Horst) - 2017-01-28 19:41 +0100
                Re: Recognizers and LOCATE anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2017-01-29 16:18 +0000
                Re: Recognizers and LOCATE Andrew Haley <andrew29@littlepinkcloud.invalid> - 2017-01-31 04:21 -0600
                Re: Recognizers and LOCATE Bernd Paysan <bernd@net2o.de> - 2017-03-12 01:07 +0000
    Re: Recognizers and LOCATE albert@cherry.spenarnc.xs4all.nl (Albert van der Horst) - 2017-01-26 21:08 +0100
      Re: Recognizers and LOCATE anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2017-01-27 10:13 +0000

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