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(* Copyright Grégoire Henry 2011.
This file is free software, distributed under the MIT license.
See the file COPYING for details.
*)
(* A cluster is the finite set of recursive class instances needed for
deriving a "regular" recursive type declaration. For example:
type 'a t = A of 'a | B of 'a * 'a t | I of int t
The corresponding cluster is:
{ 'a t ; int t }.
For multiple recursives declarations, we may group clusters by the
set of free variables involved in the required instances. For
example:
type 'a t1 = ('a, int) t2
and ('a, 'b) t2 = A of 'a t1 | B of 'b deriving (Show)
Types declaration t1 and t2 share the same clusters:
{ 'a t1; ('a, int) t2 }.
This notion of clusters allows to be less restrictive with
recursive type declaration than previous version of deriving. It's
still not sufficient for handling "non-regular" datatypes like:
type 'a nested = Z of nested | S of ('a * 'a) nested
because the set of required instance would be infinite.
*)
type cluster = {
params: Type.param list;
decls: Type.decl list;
instances: (Type.name * Type.expr list) list;
}
val make: Type.decl list -> cluster list
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