Re: Syntax for label, NEW PROPOSAL

From: Markus Mottl (mottl@miss.wu-wien.ac.at)
Date: Wed Mar 15 2000 - 18:06:32 MET

  • Next message: John Prevost: "Re: Syntax for label, NEW PROPOSAL"

    > -- Problem1: labels can be reserved keywords. This is questionable
    > and it has been strongly criticised by some Caml users, especially when
    > reading in the code the awful sequence fun:begin fun ...

    Although this is a bit off-topic, I would also like to point out some
    identifier problems with polymorphic variants as they are implemented at
    the moment (maybe this could also be changed before the major release):

    First of all, the initial quote ` can be followed by whitespace - and
    worse: by comments! I feel that this is really somewhat insane, even if
    most users won't use polymorphic variants like this.

    Secondly, I am not sure whether it is such a good idea to allow lowercase
    initial letters. They can sometimes clash with keywords and here they
    really do, because (see above) of they way they are parsed. This can lead
    to syntax errors which will surely confuse beginners (and also confused me
    once...). If parsing were changed, this wouldn't be a problem anymore, but
    I think that the relation between normal variants and polymorphic ones
    should stay evident - having to use capitals for the first letter with both
    of them seems more regular to me.

    > -- Problem2: labels that spread all over the standard libraries, even
    > when they do not add any good. I would cite:
    >
    > * labels that prevent you to use comfortably your traditional functions.
    > This is particularly evident for the List.map or List.fold_right
    > higher-order functionals.

    I fully agree - labels in higher order functions make their application
    really a pain, especially if one wants to use curried functions. Being able
    to just pass the name of functions as argument is one of the major
    "features" of functional languages - it's probably not worse the extra type
    checking information to lose it.

    What concerns syntax: I would also rather prefer the version with ":"...

    > Do not forget the design decision that has always been used before in
    > the development of Caml: interesting but not universal extensions to
    > the language must carefully be kept orthogonal to the core language
    > and its libraries.

    This is an aspect I particularly like about OCaml - one can try out new
    styles of programming without being forced to use them throughout.

    Regards,
    Markus Mottl

    -- 
    Markus Mottl, mottl@miss.wu-wien.ac.at, http://miss.wu-wien.ac.at/~mottl
    



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