Re: Recognizer for quoted strings

From	Alex <alex@rivadpm.com>
Newsgroups	comp.lang.forth
Subject	Re: Recognizer for quoted strings
Date	2017-04-07 08:41 +0100
Organization	A noiseless patient Spider
Message-ID	<oc7fko$k7r$1@dont-email.me> (permalink)
References	<oc6gcl$hu1$1@dont-email.me> <oc6jr4$k0e$1@cherry.spenarnc.xs4all.nl>

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On 4/7/2017 00:43, Albert van der Horst wrote:
> In article <oc6gcl$hu1$1@dont-email.me>, Alex  <alex@rivadpm.com> wrote:
>> http://amforth.sourceforge.net/TG/recipes/Recognizer.html
>>
>> A corrected recognizer for quoted strings using the latest RFC-D spec
>> http://amforth.sourceforge.net/pr/Recognizer-rfc-D.pdf
>>
>> : pslit postpone sliteral ;
>>
>>    ' noop
>>    :noname pslit ;
>>    :noname pslit postpone pslit ;
>> dt-token: dt:string
>>
>> : rec:string ( addr len -- )
>>     swap c@ [char] " = if
>>       negate >in +!        \ move back the parse area
>>       [char] " parse
>>       dt:string            \ get up to trailing "
>>     else drop dt:null then ;
>>
>> ' rec:string get-recognizers 1+ set-recognizers
> 
> Note that for
>     "AAP NOOT MIES"
> "AAP is passed to the recognizer conglomerate.
> Then we have multiple cases and one is to decide to go
> back and go parsing for the &" anyway.
> 
> Compare this to the prefix solution:
> 
> : " POSTPONE SKIP &" PARSE $, $@ POSTPONE DLITERAL ; PREFIX IMMEDIATE
> 
> (The skip is there to skip over the string in compile mode.)
> That is all, to add strings, in hindsight, as a loadable extension.
> 
> What is separated off is " directly, as it should be.
> No manipulation with execution tokens. " is almost a regular
> word. No data structures to hold all those execution tokens.
> Just PREFIX and one line in (FIND).

The recognizer shown allows postponing strings, and recognizers can be 
built out of regular Forth.

> 
> Of course the recognizers can do more. Stuff I don't want like
> the trailing H for hex as in intel's 80004E5AH.

If you don't like it, don't do it.

> 
> If we must complicate Forth than with words that parse ahead,
> not back and Forth.

That's just a matter of taste, since "AAP NOOT MIES" ends up as a 
address & length pair whatever system is used, and no animals or small 
children are harmed in the process.

> 
>> --
>> Alex


-- 
Alex

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Recognizer for quoted strings Alex <alex@rivadpm.com> - 2017-04-06 23:47 +0100
  Re: Recognizer for quoted strings albert@cherry.spenarnc.xs4all.nl (Albert van der Horst) - 2017-04-07 01:43 +0200
    Re: Recognizer for quoted strings Alex <alex@rivadpm.com> - 2017-04-07 08:41 +0100

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