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Different behavior between eval "07" and eval "08"
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Subject Author Date
Different behavior between eval "07" and eval "08" Liang Wang 02-01-2008
Posted by Liang Wang on February 1, 2008, 9:59 pm
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 eval "07" gets 7 but eval "08" gets an undefined value. I tested perl
5.8.8 on fedora 8 and ubuntu.

Is there any difference between those two eval statements? Is this a
bug?


Posted by John W. Krahn on February 1, 2008, 10:19 pm
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 Liang Wang wrote:
> eval "07" gets 7 but eval "08" gets an undefined value. I tested perl
> 5.8.8 on fedora 8 and ubuntu.
>
> Is there any difference between those two eval statements? Is this a
> bug?

No, there is no difference in the eval statements. The problem is that
"08" is not a valid octal number.


John
--
Perl isn't a toolbox, but a small machine shop where you
can special-order certain sorts of tools at low cost and
in short order. -- Larry Wall

Posted by Liang Wang on February 1, 2008, 10:27 pm
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> Liang Wang wrote:
> > eval "07" gets 7 but eval "08" gets an undefined value. I tested perl
> > 5.8.8 on fedora 8 and ubuntu.
>
> > Is there any difference between those two eval statements? Is this a
> > bug?
>
> No, there is no difference in the eval statements. The problem is that
> "08" is not a valid octal number.
>
> John
> --
> Perl isn't a toolbox, but a small machine shop where you
> can special-order certain sorts of tools at low cost and
> in short order. -- Larry Wall

Got it. Thanks.

I've tested "06", but not "09". What I really want to do is to
transform string "08" to integer 8. But in this case, eval doesn't
treat "08" as string, as you said.

Posted by John W. Krahn on February 2, 2008, 12:59 am
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Liang Wang wrote:
>> Liang Wang wrote:
>>> eval "07" gets 7 but eval "08" gets an undefined value. I tested perl
>>> 5.8.8 on fedora 8 and ubuntu.
>>> Is there any difference between those two eval statements? Is this a
>>> bug?
>> No, there is no difference in the eval statements. The problem is that
>> "08" is not a valid octal number.
>
> Got it. Thanks.
>
> I've tested "06", but not "09". What I really want to do is to
> transform string "08" to integer 8. But in this case, eval doesn't
> treat "08" as string, as you said.

The string "08" is already the integer 8.

$ perl -le' $x = "08"; print $x; print $x + 1'
08
9



John
--
Perl isn't a toolbox, but a small machine shop where you
can special-order certain sorts of tools at low cost and
in short order. -- Larry Wall

Posted by Tad J McClellan on February 2, 2008, 7:21 am
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> What I really want to do is to
> transform string "08" to integer 8.


Why do you think you need to transform string "08" to integer 8?

Values in Perl are both strings and numbers simultaneously.

You really should review the "Scalar values" and
"Scalar value constructors" sections in perldata.pod.


--
Tad McClellan
email: perl -le "print scalar reverse qq/moc.noitatibaher0cmdat/"

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