in reply to One liner to Check and undef hash elements

I'm sure somebody else will come up with something more optimal...

#1. 
if ((scalar grep {defined} values %{$hash}) == 0) {
   # all values are undef
}

#2.
$hash = { map {$_ => undef} keys %{$hash} };
# now empty

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Update: Changed > 0 to == 0, since the poster asked for "check if empty"

Update: Fixed precedence problem (pointed out by original poster). Works now.

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Re: Re: hash problem
by Anonymous Monk on Apr 16, 2003 at 00:53 UTC
    Hi crenz, thanks for you reply. #2 works very nicely, but I can't make #1 work. Your code prints "empty" for both of these hashes. 
    $hash->{'a'} = 1;
$hash->{'b'} = undef;
$hash->{'c'} = undef;
$hash->{'d'} = undef;
if (scalar grep {defined} values %{$hash} == 0) {
   print "empty\n";
}

$hash->{'a'} = undef;
$hash->{'b'} = undef;
$hash->{'c'} = undef;
$hash->{'d'} = undef;
if (scalar grep {defined} values %{$hash} == 0) {
   print "empty\n";
}

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