From: Stefan Monnier <monnier@iro.umontreal.ca>
To: Lars Magne Ingebrigtsen <larsi@gnus.org>
Cc: Reuben Thomas <rrt@sc3d.org>, 9222@debbugs.gnu.org
Subject: bug#9222: 23.3.50; "void" is not "typeless" (but thanks for the koan!)
Date: Sat, 10 Sep 2011 23:25:10 -0400 [thread overview]
Message-ID: <jwvvcszsr81.fsf-monnier+emacs@gnu.org> (raw)
In-Reply-To: <m3zkib7sac.fsf@stories.gnus.org> (Lars Magne Ingebrigtsen's message of "Sun, 11 Sep 2011 03:59:39 +0200")
>> In semantic/bovine/c-by.el there’s the following description:
>> ("void" summary "Built in typeless type: void")
>> Cute, but inaccurate: void is a type alright. I suggest changing
>> “typeless type” to “empty type”.
> I don't quite think that "empty type" is more meaningful than "typeless
> type". At least to me, "typeless type" makes more sense, even if it is
> somewhat humorous.
I beg to disagree: to a large extent, a type can be thought of as a set
of values. So a type can be empty (meaning that there is no value of
that type). But a "typeless type" is rather meaningless (in type
theory, types have themselves a type, so for example "1" has type "Int"
and "Int" has type "Type", but then a type can't be "typeless" since the
"definition" of a type is then basically "has type Type").
Stefan
PS: Of course, in C the "void" type is more like the "unit" type than
like the empty type, i.e. a type with a single value which hence doesn't
carry any information. E.g. a function that returns a type void can
return, tho its return value carries no information ("it returns
nothing") whereas a function that returns the empty type is a function
that will never return (since there is no value in the empty type, the
function can never return a value of the right type).
next prev parent reply other threads:[~2011-09-11 3:25 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-08-02 13:12 bug#9222: 23.3.50; "void" is not "typeless" (but thanks for the koan!) Reuben Thomas
2011-09-11 1:59 ` Lars Magne Ingebrigtsen
2011-09-11 3:25 ` Stefan Monnier [this message]
2011-09-11 3:30 ` Lars Magne Ingebrigtsen
2011-09-11 4:56 ` Stefan Monnier
2011-09-11 8:13 ` Reuben Thomas
2011-09-11 8:45 ` Andreas Schwab
2011-09-11 14:38 ` Drew Adams
2011-09-12 12:39 ` Stefan Monnier
2019-10-14 16:08 ` Stefan Kangas
2019-10-14 19:01 ` Stefan Monnier
2019-10-14 19:38 ` Stefan Kangas
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