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To: Caml List <caml-list@inria.fr>
From: Joel Reymont <joelr1@gmail.com>
Subject: Transforming of ASTs and polymorphic variants
Date: Wed, 25 Apr 2007 05:19:00 +0100
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X-Spam: no; 0.00; transforming:01 variants:01 constructors:01 variants:01 polymorphic:01 polymorphic:01 beginners:01 constructor:01 integer:01 integer:01 boolean:02 boolean:02 modules:02 conv:02 string:02 

My apologies if this is a beginners question...

I have two ASTs in different modules that look very much alike in  
that some constructors have the same name and type name. When I  
transform that ASTs I end up "re-applying" the similarly named  
constructor and arguments. This is best explained with an example.

a.ml:

type typ =
   | Integer
   | Double
   | String
   | Boolean

b.ml:

type ty =
   | Integer
   | Double
   | String
   | Boolean
   | Void

A transformation function would be

let conv_type = function
   | A.Integer -> B.Integer
   | A.String -> B.String
   | A.Boolean -> B.Boolean

I don't want to share types between ASTs since, like above, some of  
them may be supersets of others. How can I improve this with  
polymorphic variants?

	Thanks, Joel

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