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Re: Syntax for label, NEW PROPOSAL
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Date: -- (:)
From: Markus Mottl <mottl@m...>
Subject: 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 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.

Markus Mottl

Markus Mottl,,