From: Alessandro Baretta <alex@baretta.com>
To: Ocaml <caml-list@inria.fr>
Subject: [Caml-list] Typing problem with polymorphic variants
Date: Tue, 01 Apr 2003 19:34:24 +0200 [thread overview]
Message-ID: <3E89CDA0.7090200@baretta.com> (raw)
This just baffles me.
> Values do not match:
> val feature :
> [> `Clear | `Length of int | `Pitch of int
> | `Width of 'a] -> string
> is not included in
> val feature : [> `Clear] -> string
Why are "match-anything" functions of the kind of
let f = function
| `Foo -> "foo"
| `Bar -> "bar"
| _ -> "?"
incompatible with signatures like
val f : [> `Foo ] -> string
?
There clearly is no case when a value of type [> `Foo] will
not be acceptable for f. So why does the type checker reject
this?
Alex
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next reply other threads:[~2003-04-01 18:28 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2003-04-01 17:34 Alessandro Baretta [this message]
2003-04-01 18:38 ` Ville-Pertti Keinonen
2003-04-01 17:56 ` Alessandro Baretta
2003-04-01 18:44 ` David Brown
2003-04-02 1:34 ` Jacques Garrigue
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