Re^3: Common hash keys

Actually, there's no need to be careful or test for definedness.

List::Util::first() returns the result of the code block, in this case the boolean return of the exists function. The values associated with the keys never come into it.

use List::Util qw[ first ];;
my $a = { a=>0, b=>0, c=>0 }; 
my $b = { c=>0, d=>0, e=>0 };

if( first{ exists $b->{ $_ } } keys %$a ) { 
    print "Common keys!";
}
Common keys!
[download]

Examine what is said, not who speaks -- Silence betokens consent -- Love the truth but pardon error.

"Science is about questioning the status quo. Questioning authority".

In the absence of evidence, opinion is indistinguishable from prejudice.

"Too many [] have been sedated by an oppressive environment of political correctness and risk aversion."

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Re^4: Common hash keys by tinita (Parson) on Jun 08, 2008 at 12:11 UTC
List::Util::first() returns the result of the code block, in this case the boolean return of the exists function. i think it returns the key it's iterating over, just like grep works. from the docs: "first returns the first element where the result from BLOCK is a true value." `use List::Util qw[ first ]; my $a = { 0 => 0 }; my $b = { 0 => 0 }; if( first{ exists $b->{ $_ } } keys %$a ) { print "Common keys!"; }` [download] prints nothing.	[reply] [d/l]
Re^5: Common hash keys by BrowserUk (Patriarch) on Jun 08, 2008 at 15:51 UTC
Of course it does. Values of keys vs. values associated with keys. Sometimes I can be semantically blind. (Ie. plain wrong!) Examine what is said, not who speaks -- Silence betokens consent -- Love the truth but pardon error. "Science is about questioning the status quo. Questioning authority". In the absence of evidence, opinion is indistinguishable from prejudice. "Too many [] have been sedated by an oppressive environment of political correctness and risk aversion."	[reply]