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Article #2140

Re: local type not allowed as template-arg -- why??

#2140
From: David Vandevoorde
Date: Fri, 06 Oct 1995 18:55
28 lines
1712 bytes
>>>>> "MK" == Mumit Khan <khan@xraylith.wisc.edu> writes:
MK> In a recent thread in c.l.c++, James Kanze and Fabrice Clerc just 
MK> pointed out to me section 14.8.4 of the DWP which says the following:
MK> =====
MK>   14.8  Template arguments                                    [temp.arg]

MK> 4 Nor is a local type or a type with no linkage name an acceptable  tem-
MK>   plate-argument.  [Example:
MK>           void f()
MK>           {
MK>               struct S { /* ... */ };                     
MK>               X<S,p> x3; // error: local type used as template-argument
MK>           }
MK>    --end example] 
MK> =====
MK> Why is this necessary? Why isn't the template argument S in X<S,p>
MK> simply treated as X<f()::S, p> (or something along these lines)?

I think this is because the point of instantiation is immediately
_before_ the ``enclosing scope for the point of first use'' (see
[temp.point] 14.3.2/1 for exact wording; also /6 and the rest of
that section).

	Daveed
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Message-ID: <VANDEVOD.95Oct6144945@avs.cs.rpi.edu>
Path: arc1-ca.pugleaf.net!in2.uu.net!bounce-back
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Path: arc1-ca.pugleaf.net!in2.uu.net!bounce-back
Date: 06 Oct 95 18:55:42 GMT
Approved: fjh@cs.mu.oz.au
From: vandevod@cs.rpi.edu (David Vandevoorde)
Newsgroups: comp.std.c++
Subject: Re: local type not allowed as template-arg -- why??
X-Original-Date: 06 Oct 1995 18:49:45 GMT
Organization: RPI Computer Science
Message-ID: <VANDEVOD.95Oct6144945@avs.cs.rpi.edu>
References: <4529o8$1bfa@news.doit.wisc.edu>
In-Reply-To: khan@xraylith.wisc.edu's message of 06 Oct 95 04:58:29 GMT