From: Michael Vanier <mvanier@cs.caltech.edu>
To: caml-list@inria.fr
Subject: [Caml-list] simple typing question
Date: Mon, 1 Jul 2002 21:14:35 -0700 [thread overview]
Message-ID: <200207020414.g624EZf05386@orchestra.cs.caltech.edu> (raw)
I imagine this has been asked and answered before, so I apologize in
advance.
Compare these two functions:
# let f x = List.map (fun y -> y) x ;;
val f : 'a list -> 'a list = <fun>
and
# let f = List.map (fun y -> y) ;;
val f : '_a list -> '_a list = <fun>
Why does the second use the '_a type variable instead of 'a? I thought
that special type variables only had to do with polymorphic references.
The FAQ states that the latter expression can't be generalized, but I don't
really understand why.
Mike
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next reply other threads:[~2002-07-02 8:49 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2002-07-02 4:14 Michael Vanier [this message]
2002-07-02 9:14 ` Pierre Weis
2002-07-02 9:49 ` Michael Vanier
2002-07-02 11:29 ` Daniel de Rauglaudre
2002-07-02 11:42 ` Xavier Leroy
2002-07-02 18:57 ` Pixel
2002-07-02 20:59 ` Pierre Weis
2002-07-03 0:39 ` Pixel
2002-07-03 1:49 ` Jacques Garrigue
2002-07-03 23:24 ` Pixel
2002-07-03 7:51 ` Francois Pottier
2002-07-03 11:25 ` Pixel
2002-07-03 18:10 ` Lauri Alanko
2002-07-02 14:56 ` Pierre Weis
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