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Re: ++ turns undef into 0 first

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Rafael Garcia-Suarez
August 19, 2005 02:41
Re: ++ turns undef into 0 first
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On 8/18/05, Peter Scott <> wrote:
> This recently bit me:
> $ perl -wle 'print 42 if defined($h{foo}++)'
> 42
> Now, before thousands of you reach for the flamethrowers, yes, I know
> - now - that this is documented.  I found it in perlop right where it
> ought to be:
> | undef is always treated as numeric, and in particular is changed to 0
> | before incrementing (so that a post-increment of an undef value will
> | return 0 rather than undef).

This was documented by Hugo as change 19014 :
Hugo, any comment on this ?

> The only thing that perturbs me is that I had to find this after I was
> starting to wonder whether there was a bug.  So this looks to me like
> suboptimal behavior that has been documented; any chance of making it
> behave the more logical way, i.e., that the expression evaluates to the
> original value and not some modified one?  I can't imagine there is much
> code relying on the current behavior.

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