From: "Mark Shinwell" <mshinwell@janestcapital.com>
To: Aaron Bohannon <bohannon@cis.upenn.edu>
Cc: caml-list@inria.fr
Subject: Re: [Caml-list] annotations and type-checking
Date: Wed, 29 Jul 2009 08:40:50 +0100 [thread overview]
Message-ID: <20090729074050.GK19609@janestcapital.com> (raw)
In-Reply-To: <c413fcb70907281447l1f6c3d0y21c3fa024ac45791@mail.gmail.com>
On Tue, Jul 28, 2009 at 05:47:25PM -0400, Aaron Bohannon wrote:
> Why do the first two programs type-check but the thrid one does not?
Dark corners of the type system.
> let f (x : 'a) : 'a = x in (f true, f 3);;
Explicit type variables in this situation are considered "global". They are
not generalized until the type of the whole toplevel declaration has been
determined. Consequentially, during type-checking of the body of your
let expression, 'a is not a generalized variable.
There is more detail on similar situations here:
http://caml.inria.fr/pub/ml-archives/caml-list/2002/06/a03da53be62c12671a891708c51e85f9.en.html
Mark
next prev parent reply other threads:[~2009-07-29 7:40 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2009-07-28 21:47 Aaron Bohannon
2009-07-28 23:28 ` [Caml-list] " Jon Harrop
2009-07-28 23:04 ` Philippe
2009-07-29 5:38 ` Johannes Kanig
2009-07-29 7:40 ` Mark Shinwell [this message]
2009-07-29 13:41 ` Aaron Bohannon
2009-07-29 14:39 ` Jacques Garrigue
2009-07-29 16:50 ` Aaron Bohannon
2009-07-29 19:01 ` Jon Harrop
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