Re: Languages with optional spaces

From	Gene <gene.ressler@gmail.com>
Newsgroups	comp.compilers
Subject	Re: Languages with optional spaces
Date	2020-04-14 10:08 -0700
Organization	Compilers Central
Message-ID	<20-04-007@comp.compilers> (permalink)
References	<20-02-015@comp.compilers>

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On Wednesday, February 19, 2020 at 11:24:02 AM UTC-5, Maury Markowitz wrote:
> I'm trying to write a lex/yacc (flex/bison) interpreter for classic BASICs
> like the original DEC/MS, HP/DG etc. ...
>
> The problem is that FORI part. Some BASICs allow variable names with more than
> two characters, so in theory, FORI could be a variable. ...

> Is there a canonical cure for this sort of problem that isn't worse than the
> disease?

Flex regexes alone don't have enough power. But you could add a conditional
REJECT when a normal ID match has a prefix that's a keyword. (This could be
made fast with a trie of that's an issue.) REJECT causes fallback to the "next
best" rule, which seems to be what you want.

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Languages with optional spaces Maury Markowitz <maury.markowitz@gmail.com> - 2020-02-19 07:35 -0800
  Re: Languages with optional spaces Jerry <awanderin@gmail.com> - 2020-02-20 23:38 -0700
    Re: Languages with optional spaces Maury Markowitz <maury.markowitz@gmail.com> - 2020-02-25 06:13 -0800
      Re: Languages with optional spaces awanderin <awanderin@gmail.com> - 2020-02-26 10:03 -0700
    Re: Languages with optional spaces "Ev. Drikos" <drikosev@gmail.com> - 2020-03-12 17:45 +0200
  Re: Languages with optional spaces "Ev. Drikos" <drikosev@gmail.com> - 2020-02-23 12:33 +0200
    Re: Languages with optional spaces Martin Ward <martin@gkc.org.uk> - 2020-02-25 17:00 +0000
      Re: Languages with optional spaces "Ev. Drikos" <drikosev@gmail.com> - 2020-02-28 13:34 +0200
    Re: Languages with optional spaces Christopher F Clark <christopher.f.clark@compiler-resources.com> - 2020-02-29 11:48 +0200
      Re: Languages with optional spaces "Ev. Drikos" <drikosev@gmail.com> - 2020-02-29 21:38 +0200
        Re: Languages with optional spaces Christopher F Clark <christopher.f.clark@compiler-resources.com> - 2020-03-01 10:07 +0200
        Re: Languages with optional spaces "Ev. Drikos" <drikosev@gmail.com> - 2020-03-01 19:41 +0200
          Re: Languages with optional spaces Christopher F Clark <christopher.f.clark@compiler-resources.com> - 2020-03-02 08:33 +0200
            Re: Languages with optional spaces "Ev. Drikos" <drikosev@gmail.com> - 2020-03-02 20:04 +0200
      Re: Languages with optional spaces Hans-Peter Diettrich <DrDiettrich1@netscape.net> - 2020-03-01 00:28 +0100
  Re: Languages with optional spaces Maury Markowitz <maury.markowitz@gmail.com> - 2020-02-25 06:11 -0800
  Re: Languages with optional spaces Kaz Kylheku <493-878-3164@kylheku.com> - 2020-02-26 08:06 +0000
  Re: Languages with optional spaces and tools Hans-Peter Diettrich <DrDiettrich1@netscape.net> - 2020-02-28 20:16 +0100
  Re: Languages with optional spaces gah4@u.washington.edu - 2020-03-02 21:12 -0800
  Re: Languages with optional spaces Gene <gene.ressler@gmail.com> - 2020-04-14 10:08 -0700
  Re: Languages with optional spaces mertesthomas@gmail.com - 2020-04-19 04:04 -0700
  Re: Languages with optional spaces aston.goldsmith@gmail.com - 2020-05-05 13:05 -0700

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