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Re: Articles/books that discuss separating the context-free part of a language from the context-sensitive part?

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"Costello, Roger L." <costello@mitre.org> writes:
>The poster makes the point that most programming languages define a
>context-free core, and then have additional algorithms which run on the parse
>tree to filter out constructs that are illegal in the language:
...
>[ [...] it also permits much better
>error messages. -John]

That depends on the syntax of the language.  E.g., at one time
Modula-2 was the language used in our introductory programming course
25 years ago, our students used to write things like

a<3 AND b<3

and the compiler reported a type error (a and b were of type INTEGER).
But it really was a syntax error.  The students should have written

(a<3) AND (b<3)

because the implicit binding was

a<(3 AND b)<3

and "3 AND b" was a type error.  This error message confused the
students no end.

- anton
--
M. Anton Ertl
anton@mips.complang.tuwien.ac.at
http://www.complang.tuwien.ac.at/anton/

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Articles/books that discuss separating the context-free part of a language from the context-sensitive part? "Costello, Roger L." <costello@mitre.org> - 2013-05-17 20:57 +0000
  Re: Articles/books that discuss separating the context-free part of a language from the context-sensitive part? glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2013-05-18 00:18 +0000
    Re: Articles/books that discuss separating the context-free part of a language from the context-sensitive part? Gene Wirchenko <genew@telus.net> - 2013-05-19 18:02 -0700
      Re: Articles/books that discuss separating the context-free part of a language from the context-sensitive part? glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2013-05-20 03:17 +0000
  Re: Articles/books that discuss separating the context-free part of a language from the context-sensitive part? Aleksey Demakov <ademakov@gmail.com> - 2013-05-18 16:52 +0400
  Re: Articles/books that discuss separating the context-free part of a language from the context-sensitive part? anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2013-05-20 10:53 +0000
    Re: Articles/books that discuss separating the context-free part of a language from the context-sensitive part? Gene Wirchenko <genew@telus.net> - 2013-05-20 23:24 -0700
    precedence have both ways jgk@panix.com (Joe keane) - 2013-05-30 23:21 -0400
      Re: precedence have both ways glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2013-05-31 05:10 +0000
      Re: precedence have both ways anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2013-05-31 10:54 +0000

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