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Busin
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 Posted: Tue Jun 29, 2004 7:29 am Post subject: Using valarray |
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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<bool> 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!
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John Harrison
Guest
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| Posted: Tue Jun 29, 2004 8:19 am Post subject: Re: Using valarray |
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"Busin" <businm (AT) fidrep (DOT) com> wrote
| Quote: | 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)?
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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.
| Quote: |
Can va1 be initialized like "valarray<bool> va1(10, false);" when defining
it?
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No, like this
valarray<bool> val(false, 10);
| Quote: |
Is it ok to assign va1 to va2?
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Yes
| Quote: | Does va2 have to be specified with a size
before assigning va1 to it?
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No
| Quote: | Must the size of va2 be larger than va1?
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No, va2 will change its size to be the same as va1
john
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tom_usenet
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| Posted: Tue Jun 29, 2004 8:54 am Post subject: Re: Using valarray |
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On Tue, 29 Jun 2004 09:19:49 +0100, "John Harrison"
<john_andronicus (AT) hotmail (DOT) com> wrote:
| Quote: |
"Busin" <businm (AT) fidrep (DOT) com> wrote in message
news:8T8Ec.158035$Gx4.68371 (AT) bgtnsc04-news (DOT) ops.worldnet.att.net...
valarray<bool> va1(10);
// Initialize va1 here?
valarray<bool> va2 (80);
va2 = va1;
Is it ok to assign va1 to va2?
Yes
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No, it's undefined behaviour, since the lengths don't match.
| Quote: | Does va2 have to be specified with a size
before assigning va1 to it?
No
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Yes.
| Quote: | Must the size of va2 be larger than va1?
No, va2 will change its size to be the same as va1
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The sizes of va2 and va1 must be exactly the same. See 26.3.2.2.
Tom
--
C++ FAQ: http://www.parashift.com/c++-faq-lite/
C FAQ: http://www.eskimo.com/~scs/C-faq/top.html
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John Harrison
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| Posted: Tue Jun 29, 2004 11:04 am Post subject: Re: Using valarray |
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"tom_usenet" <tom_usenet (AT) hotmail (DOT) com> wrote
| Quote: | On Tue, 29 Jun 2004 09:19:49 +0100, "John Harrison"
[email]john_andronicus (AT) hotmail (DOT) com[/email]> wrote:
"Busin" <businm (AT) fidrep (DOT) com> wrote in message
news:8T8Ec.158035$Gx4.68371 (AT) bgtnsc04-news (DOT) ops.worldnet.att.net...
valarray<bool> va1(10);
// Initialize va1 here?
valarray<bool> va2 (80);
va2 = va1;
Is it ok to assign va1 to va2?
Yes
No, it's undefined behaviour, since the lengths don't match.
Does va2 have to be specified with a size
before assigning va1 to it?
No
Yes.
Must the size of va2 be larger than va1?
No, va2 will change its size to be the same as va1
The sizes of va2 and va1 must be exactly the same. See 26.3.2.2.
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OK, must have been getting confused with vector. Apologies.
john
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