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[Caml-list] :: operator not quotable using ( ... )
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Date: 2002-04-24 (10:56)
From: Remi VANICAT <vanicat@l...>
Subject: Re: [Caml-list] :: operator not quotable using ( ... )
John Prevost <> writes:

> When writing an example just now for this list, I noticed that you can
> no longer (assuming you ever could) write (::) or any variation
> thereof to refer to the definition of the :: cons operator.  Since
> there is no other standard way to write this, one must use:

cons is not really an operator, it's a constructor

> let cons x y = x :: y

the same hold for any constructor :

moi@debian:~/prog/ocaml-cvs$ ocaml
        Objective Caml version 3.04

# type foo =
    Bar of int * int;;
type foo = Bar of int * int
# Bar;;
The constructor Bar expects 2 argument(s),
but is here applied to 0 argument(s)

you have to write

let bar x y = Bar (x, y)

> to get one.  This is unfortunate when you wish to, say, define map in
> terms of fold.  My suspicion is that it may have worked in the past,
> but broken by keyword argument parsing.  Is there any chance (::)
> could be special cased to work correctly, even though it conflicts
> with (x : y) for typing?  I don't think it likely that anybody would
> write (::) intending to express a type.

I don't know, but the true problem is the possibility to implicitly
define function that correspond to constructor.

Rémi Vanicat
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