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Date: Wed, 26 Oct 2011 16:07:12 -0400
From: John Carr <jfc@mit.edu>
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Subject: [Caml-list] Defeating the value restriction


Can I rewrite this function to have the type I requested
instead of failing type checking?

let f : ('a * 'a -> 'a) -> int * bool = fun x -> x (0,1), x (true,false)

I assume the type error is caused by the value restriction.
The parameter (x) becomes monomorphic when applied, so it
can not be applied to both types (int*int) and (bool*bool).

A top level syntactic function

let x : ('a * 'a -> 'a) = fun (a,b) -> a

retains its original, generalized type under similar circumstances.

My real example that fails type checking is more complicated.
I believe the root cause is the same.

    --John Carr (jfc@mit.edu)