Re: syntax extension, was Why context-free?

"toby" <toby@telegraphics.com.au>
1 Nov 2005 00:22:34 -0500

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Re: syntax extension, was Why context-free? haberg@math.su.se (2005-11-02)
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[7 later articles]
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From: "toby" <toby@telegraphics.com.au>
Newsgroups: comp.compilers
Date: 1 Nov 2005 00:22:34 -0500
Organization: http://groups.google.com
References: 05-10-05305-10-061 05-10-062 05-10-068 05-10-075
Keywords: parse, design

Nick Maclaren wrote:
> glen herrmannsfeldt <gah@ugcs.caltech.edu> wrote:
> >John wrote:
> > > [
> >> diagnostics and general readability. When you start building types
> >> into the syntax, that means that many type errors now are likely to
> >> produce "syntax error" rather than "string found where boolean
> >> expected", and I have to say your 2 vs. 3 way branch is grosser than
> >> anything I've done in perl. As far as extending the syntax on the
> >> fly, that avenue was extensively investigated in the 1970s in
> >> languages like IMP-72 and EL/1, all of which died.
> >
> >Two languages that I have used recently that allow syntax changes, TeX
> >and mathematica, don't seem to be going away so fast.
>
> Not to say Lisp :-)
>
> >There are some very strange errors that you can get in both languages.
>
> Yes, indeed. TeX, in particular, is ghastly - but that has little
> to do with its extensibility. ...


But TeX (like METAFONT) is closely tailored to its domain, and within
that domain, is quite elegant. Of course it can be 'ghastly' for tasks
of a different character - Knuth himself gives several examples in The
TeXbook. Anything is *possible* but not necessarily easy.


Similarly I find that many people who complain about Perl - especially
comparing it to languages such as Ruby or Python - have missed the
point. Perl has its sweet spot domains (as a child of sed, C, sh, etc)
and while it is a powerful general purpose programming language, that
was not its guiding principle. It was highly adapted from birth.


--Toby


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