[wg-camlp4] Changes to the parsetree

[Gerd Stolpmann]

Am 25.03.2013 19:49:49 schrieb(en) Alain Frisch:
> On 03/25/2013 03:13 PM, jathdr wrote:
>> Could we get a summary of the current syntax proposal? I've been
>> following along, but I'm a bit lost as to what has been discussed,
>> accepted, rejected, etc.
> 
> This file describes the current syntax proposal:
> 
> http://caml.inria.fr/cgi-bin/viewvc.cgi/ocaml/branches/extension_points/experimental/frisch/extension_points.txt?revision=HEAD&view=markup

Two little comments:

  - So far, a begin/end pair can always be replaced by normal  
parentheses.
    The "keyword" rules do not allow it so far - when we have
    begin [@foo] ... end, why not also allow ([@foo] ...) ?

    (Currently, it's even possible to use begin/end and parentheses
    in a mixed way, like ( ... end - maybe also get rid of this
    asymmetry, as we are at syntax?)

  - Am I right that we get a new form of commenting out code blocks?

    (* {ignore| commented out text can almost contain anything |ignore}  
*)

    That would be helpful to comment out blocks that violate the lexing
    rules.



> 
>> This is probably a bit off topic, but while we're talking about
>> interval patterns: I discovered the other day that interval patterns
>> only work for chars, while I always assumed they also worked for
>> ints. Is there a reason why they don't?
> 
> Currently, range patterns for characters are expanded in the parser.  
> Doing so for integers as well could lead to huge or-patterns to be  
> processed by the rest of the compiler.  Supporting range patterns  
> directly in the compiler would add a little bit of extra complexity  
> for type-checking (exhaustiveness check) and code generation.  I  
> don't see any theoretical problem, though.
> 
> 
> -- Alain
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Gerd Stolpmann, Darmstadt, Germany    gerd at gerd-stolpmann.de
Creator of GODI and camlcity.org.
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