Re: [Caml-list] Newbie comment on constructor syntax

[Hendrik Boom <hendrik@topoi.pooq.com>]

On Mon, Nov 09, 2015 at 08:09:30AM +0000, Soegtrop, Michael wrote:
> Dear Florian, Norman, 
> 
> > > Curiously, the argument is not really a tuple.  This does not work:
> > >
> > > type x = X of int * int
> > > let c = (1, 2) in X c
> > 
> > However the following works:
> > # type x  = X of (int * int);;
> > type x = X of (int * int)
> > # let c = (1, 2) in X c;;
> > - : x = X (1, 2)
> 
> Exactly this is what is quite confusing (for the beginner): constructors are a rather odd mix of multiple arguments and tuples. The notation looks like tuples, both in definition and use, but it isn't. And it is not a multiple argument function either, since currying doesn't work. That adding parenthesis makes it a real tuple doesn't make it better, since at some other places a*b and (a*b) are the same.
> 
> To me this is quite a scar in the beauty of the language - the kind of thing you can't avoid to look at, if you know what I mean. Of cause it is not really an issue. It is just way disappointing for new users to find this kind of imperfection and it gives a little dent in the enthusiasm. But just a little one ;-)

Parentheses should never be used with a meaning other than indicating 
proper grouping, their original function in high school algebra.
OCaml went partway there by abolishing them as syntax for function 
calls.

-- hendrik