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I'm trying to check whether the given key exists in the hash.
The simple example:

use feature ':5.10';

my %a = (a => 1, b => 2);
say %a ~~ 'a' ? 'YES' : 'NO'; # says NO -- why?
say %a ~~ 'c' ? 'YES' : 'NO'; # says NO
say 'a' ~~ %a ? 'YES' : 'NO'; # says YES
say 'c' ~~ %a ? 'YES' : 'NO'; # says NO

There is a description of smart mathing operator:
http://search.cpan.org/~rgarcia/perl-5.10.0-RC1/pod/perlsyn. pod#Smart_matching_in_detail
"...The behaviour of a smart match depends on what type of thing its
arguments are. It is always commutative, i.e. |$a ~~ $b| behaves the
same as |$b ~~ $a|..."

Why is the result of %a ~~ 'a' differs from the result of 'a' ~~ %a ?


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>>>>> "VDB" == Vladimir D Belousov <maillist [at] klarnet.ru> writes:

VDB> I'm trying to check whether the given key exists in the hash.

smart matching is powerful and cool but why don't you just call exists
on the hash key? there is no win to using smart matching for that. it is
included for consistancy but it isn't needed for hash keys.

uri

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19.01.2011 0:09, Uri Guttman пишет:
> but why don't you just call exists on the hash key? there is no win to
> using smart matching for that. it is included for consistancy but it
> isn't needed for hash keys.
>

I just want to understand how does it work :)


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The smart match is no longer commutative - That was removed after 5.10.1, I
think.

http://www.learning-perl.com/?p=32
http://perldoc.perl.org/perlsyn.html#Smart-matching-in-detai l

Brian.

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19.01.2011 0:43, Brian Fraser пишет:
> The smart match is no longer commutative - That was removed after 5.10.1, I
> think.
>
> http://www.learning-perl.com/?p=32
> http://perldoc.perl.org/perlsyn.html#Smart-matching-in-detai l
>
> Brian.
>
Thank you!


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