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From: Nicolas Ojeda Bar <nojb@math.harvard.edu>
Subject: extending records with Obj.magic
Date: Mon, 30 Aug 2010 17:04:22 -0400
To: caml-list@yquem.inria.fr
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X-Spam: no; 0.00; extensible:01 int:01 int:01 seems:03 types:05 generated:05 extension:06 nicolas:08 mess:09 actually:10 magic:10 magic:10 obj:11 obj:11 supposedly:11 

Hello,

I need extensible records, and the code below seems to
work. Are there any pitfall that I should be aware of?
Could this mess up the GC?

# type t0 = { a : int };
# type t1 = { a2 : int; b : int };
# value x1 = { a2 = 3; b = 5 };
# value x0 : t0 = Obj.magic x1;
value x0 = { a = 3 }
# value x0' : t1 = Obj.magic x0;
value x0' = { a2 = 3; b = 5 }

(supposedly t1 is an extension of t0). The types are
being generated by a program, so I am not worried about
actually having to _write_ this myself.

Thanks!
N