Re: setting values in anonymous hash

There comes a time when one must display one's ignorance without fear. I suspect this is my time :)

I think I am missing something fundamental. First, I don't see why %tmp is necessary, nor do I I understand resetting the $k and $v before the while loop starts over -- don't they get reset automatically?

In other words, why wouldn't this work:

while (my $ref2 = $sth2->fetchrow_hashref()) {
  while (my ($k, $v) = each %$ref2) {
    $ref2->{$k} = '' if $v == undef;
  }
}
[download]

Comment on Re: setting values in anonymous hash Download Code

Replies are listed 'Best First'.
Re: Re: setting values in anonymous hash by Dominus (Parson) on Nov 28, 2000 at 19:50 UTC
Says snax: > why wouldn't this work: > `$ref2->{$k} = '' if $v == undef;` It doesn't work because if `$v` was `"hello"`, then you have just scrubbed it out and replaced it with the empty string. You should never compare anything for equality with `undef`, because `0 == undef` is true, and `"fish" == undef` is also true. This is because `undef` behaves like 0 in a numeric context, and so do most strings. Even `"" eq undef` is true, which probably is not what you want. The only way to check to see if something is `undef` is to use the `defined` operator: `$ref2->{$k} = '' if not defined $v;` [download]	[reply] [d/l]
Re: Re: Re: setting values in anonymous hash by snax (Hermit) on Nov 28, 2000 at 19:55 UTC
Oy. That would be bad indeed. I used some test code on the command line and was having trouble getting `defined` to return false values, so settled on the equality test. Context, as always, is important, as you demonstrate most eloquently.	[reply]
Re: Re: setting values in anonymous hash by agoth (Chaplain) on Nov 28, 2000 at 18:28 UTC
that way works, ish, but just look at the warnings under -w? I had left the variable reset in by mistake! PS: works a treat though this way.... `while (my ($k, $v) = each %$ref2) { $ref2->{$k} = '' if (!defined $ref2->{$k}); } push @{ $tablist{$user_table} }, $ref2;` [download] Cheers.. PPS: and even better this way, thanks!!!! `for (keys %$ref2) { $ref2->{$_} = '' if (!defined $ref2->{$_}); } push @{ $tablist{$user_table} }, $ref2;` [download] PPPS: maybe down to one line if I was using 5.5! (untested this last one) `$ref2->{$_} = '' unless (defined $ref2->{$_}) for (keys %$ref2);` [download]	[reply] [d/l] [select]