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From: =?Windows-1252?Q?Terje_Sletteb=F8?= <tslettebo@chello.no.nospam>
Newsgroups: comp.lang.ada,comp.lang.c++.moderated
Subject: Re: C bug of the day
Date: 14 Jun 2003 20:45:17 -0400
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Date: 2003-06-14T20:45:17-04:00
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"Dave Harris" <brangdon@cix.co.uk> wrote in message
news:memo.20030613191305.38347A@brangdon.madasafish.com...
> jimmaureenrogers@att.net (James Rogers) wrote (abridged):
>  > If your suggestion was adopted, how would it affect existing
>  > programs?
>
> Some currently non-portable ones would become well-behaved.
>
>  > why would you ever *want* uninitialized variables?
>
> Mainly for speed. We would want to be able to say, eg,
>      std::vector<int> vec( 1000000, unitialised );
>
> to avoid writing a million zeros. Which I suspect makes it a
non-trivial
> language change. What is the type of "initialised"?

You could always have an overloaded constructor, with a "tag" type (as
suggested in the "using named parameters separators" thread at
comp.std.c++):

enum uninitialised_type { uninitialised };

std::vector constructor:

vector(size_t size, uninitialised_type); // Performs uninitialised
construction

Not a non-trivial language change, at all. Just a library change. An
implementation may well optimise away the tag value passing, seeing that
it's not used.


Regards,

Terje

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