Using valarray

[Busin]

valarray<bool> va1(10);

// Initialize va1 here?

valarray<bool> va2 (80);

va2 = va1;

Do we have to initialize va1 like using for loop above (since if not, the
printout of va1 will display garbage)?

Can va1 be initialized like "valarray<b ool> va1(10, false);" when defining
it?

Is it ok to assign va1 to va2? Does va2 have to be specified with a size
before assigning va1 to it? Must the size of va2 be larger than va1?

Thanks!

[John Harrison]

Re: Using valarray


"Busin" <businm@fidrep. com> wrote in message
news:8T8Ec.1580 35$Gx4.68371@bg tnsc04-news.ops.worldn et.att.net...[color=blue]
> valarray<bool> va1(10);
>
> // Initialize va1 here?
>
> valarray<bool> va2 (80);
>
> va2 = va1;
>
> Do we have to initialize va1 like using for loop above (since if not, the
> printout of va1 will display garbage)?[/color]

No, the elements of va1 will be default constructed. I believe for a bool
this should mean it will be set to false. Your compiler may not implement
this correctly though.
[color=blue]
>
> Can va1 be initialized like "valarray<b ool> va1(10, false);" when defining
> it?[/color]

No, like this

valarray<bool> val(false, 10);
[color=blue]
>
> Is it ok to assign va1 to va2?[/color]

Yes
[color=blue]
> Does va2 have to be specified with a size
> before assigning va1 to it?[/color]

No
[color=blue]
> Must the size of va2 be larger than va1?[/color]

No, va2 will change its size to be the same as va1

john

[tom_usenet]

Re: Using valarray

On Tue, 29 Jun 2004 09:19:49 +0100, "John Harrison"
<john_andronicu s@hotmail.com> wrote:
[color=blue]
>
>"Busin" <businm@fidrep. com> wrote in message
>news:8T8Ec.158 035$Gx4.68371@b gtnsc04-news.ops.worldn et.att.net...[color=green]
>> valarray<bool> va1(10);
>>
>> // Initialize va1 here?
>>
>> valarray<bool> va2 (80);
>>
>> va2 = va1;
>>
>> Is it ok to assign va1 to va2?[/color]
>
>Yes[/color]

No, it's undefined behaviour, since the lengths don't match.
[color=blue][color=green]
>> Does va2 have to be specified with a size
>> before assigning va1 to it?[/color]
>
>No[/color]

Yes.
[color=blue][color=green]
>> Must the size of va2 be larger than va1?[/color]
>
>No, va2 will change its size to be the same as va1[/color]

The sizes of va2 and va1 must be exactly the same. See 26.3.2.2.

Tom
--
C++ FAQ: http://www.parashift.com/c++-faq-lite/
C FAQ: http://www.eskimo.com/~scs/C-faq/top.html

[John Harrison]

Re: Using valarray


"tom_usenet " <tom_usenet@hot mail.com> wrote in message
news:7fb2e0ti5g 4ps5d32jtl5rr79 s4h6pi01k@4ax.c om...[color=blue]
> On Tue, 29 Jun 2004 09:19:49 +0100, "John Harrison"
> <john_andronicu s@hotmail.com> wrote:
>[color=green]
> >
> >"Busin" <businm@fidrep. com> wrote in message
> >news:8T8Ec.158 035$Gx4.68371@b gtnsc04-news.ops.worldn et.att.net...[color=darkred]
> >> valarray<bool> va1(10);
> >>
> >> // Initialize va1 here?
> >>
> >> valarray<bool> va2 (80);
> >>
> >> va2 = va1;
> >>
> >> Is it ok to assign va1 to va2?[/color]
> >
> >Yes[/color]
>
> No, it's undefined behaviour, since the lengths don't match.
>[color=green][color=darkred]
> >> Does va2 have to be specified with a size
> >> before assigning va1 to it?[/color]
> >
> >No[/color]
>
> Yes.
>[color=green][color=darkred]
> >> Must the size of va2 be larger than va1?[/color]
> >
> >No, va2 will change its size to be the same as va1[/color]
>
> The sizes of va2 and va1 must be exactly the same. See 26.3.2.2.
>[/color]

OK, must have been getting confused with vector. Apologies.

john