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To: caml-list@inria.fr
Subject: Re: [Caml-list] Constraint
References: <000701c1c9be$22947b50$e700a8c0@warp>
From: Remi VANICAT <vanicat@labri.u-bordeaux.fr>
Date: 12 Mar 2002 13:47:19 +0100
In-Reply-To: <000701c1c9be$22947b50$e700a8c0@warp>
Message-ID: <87eliq0x7s.dlv@wanadoo.fr>
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"Warp" <warplayer@free.fr> writes:

> Hi
> I had a quite big parametrized class and it takes me few hours to figure out
> where a constraint I didn't want was occuring. It's true that I'm not very
> familiar with constraints, but I think it would be nice to enable the OCaml
> compiler to print some more informations about where the constraint occurs
> in the code ( a simple line number will be enough. ) I don't know if that
> can be done, but i think that would be somehow useful.

There is a possibility to find such error. Here an example :

class type foo =
object
  method baz : int
end

class ['a] bar (f : 'a) =
object
  method buz = (f #baaz) + 1
end

here, I've done a mistake in the name of the method baz (writing it
baaz). 

I can temporally transform my code in :

class ['a] bar (f : 'a) =
object
  constraint 'a = foo

  method buz = (f #baaz) + 1
end

then, I will have a type error (no method baaz).

of course it's not a clean method, but it work.
-- 
Rémi Vanicat
vanicat@labri.u-bordeaux.fr
http://dept-info.labri.u-bordeaux.fr/~vanicat
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