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[Caml-list] Is a Cow an Animal?
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Date: 2002-04-19 (00:22)
From: Remi VANICAT <vanicat@l...>
Subject: Re: [Caml-list] Is a Cow an Animal?
james woodyatt <> writes:

> I borrowed a technique I learned here from Brian Rogoff that uses an
> abstract type with a contravariant type parameter for passing the type
> of energy a food object contains to an animal object that can eat it.
> (I wish I were smart enough to know the name for this technique.)

the use of an abstract type with a covariant or contravariant type (or
even not variant) parameter, and where the actual implementation of
the type doesn't use this parameter (as in type 'a eater = int) is
often call phantom type.

one can read the very interesting mail about this in the archive of
this mailing list

Rémi Vanicat
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