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Create a constraint between variant type and data list
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Date: 2010-09-03 (17:17)
From: Sylvain Le Gall <sylvain@l...>
Subject: Create a constraint between variant type and data list
Hello all,

I would like to somehow enforce that a variant type is associated with
an entry in a data list. 

For example, 

I would like to define:

type license = GPL | LGPL 


let data = [ GPL, "GNU Public license"; 
             LGPL, "GNU Lesser General Public license" ]

I would like to enforce that all variants of license are in the
association list.

I have tried to use polymorphic variants, but don't see how to enforce
this constraint.

The point, is that if I add a new variant to license (e.g. BSD3), the
compiler output an error because this new variant is not in data list.

Any ideas ? If you need to use another type expression rather than
variant, please do so, as long as I am able to link the license type
and data list.

Thanks all,
Sylvain Le Gall