[Israel.pm] Strange "Argument isn't numeric" warning

[Oron Peled]

On Wednesday, 2 בMay 2007 17:06, Jason Elbaum wrote:
> Can anyone explain the following phenomenon, or is it a bug in perl?
> print 5 + 7, "\n";
> print "5" + 7, "\n";
> print "5&6" + 7, "\n";
> 
> The output:
> 
> Argument "5&6" isn't numeric in addition (+) at - line 5.
> 12
> 12
> 12

Since you quoted it, it's a string. However, since it is used
in numeric context (because of +), Perl tries to convert it
to number.

Perl conversion work very similar to atof(3) [maybe it even use it, didn't
bother to check]. It convert the numeric content of the string and stops
conversion when it hits non-numeric characters.

That's why "5&6" is converted to 5 in numeric context. And for the
same reason the string "hello" is converted to 0 (conversion stops
right at the beginning of the string).

> So is "5&6" numeric or not? The warning says it isn't, but the
> addition evaluates to 12! Shouldn't non-numeric strings evaluate to
> zero?

Hope it is clear now.

-- 
Oron Peled                             Voice/Fax: +972-4-8228492
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