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Date: Mon, 7 Jun 2010 14:01:38 +0200
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Subject: Re: [Caml-list] Annotated trees
From: blue storm <bluestorm.dylc@gmail.com>
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X-Spam: no; 0.00; bunzli:01 buenzli:01 annotations:01 node:01 node:01 storm:98 polymorphic:01 wrote:01 caml-list:01 constraint:01 argument:02 tree:02 tree:02 annotated:02 annotation:02 

On Mon, Jun 7, 2010 at 11:22 AM, Daniel B=FCnzli
<daniel.buenzli@erratique.ch> wrote:
> That's true and certainly a good argument for the second form if you
> already know the type of your annotations and have such needs. However
> if you want to keep that polymorphic (the annotation is a convenience
> for the client) it results in a type variable per case which becomes
> heavy.

You probably know that already but there is a nice use of object types
as "type-level records" that make that kind of "lots of type
variables" situations tractable :

type 'annot tree =3D
 | Leaf of 'leaf_annot * string
 | Node of 'node_annot * 'annot tree list
constraint 'annot =3D
 < leaf : 'leaf_annot;
   node : 'node_annot >