Re^2: How can I re-program the exists function?

Well, as I said it was easier to explain using the exists example, but basically, my goal is to test an entry from a hashref, these entries contains objects and I wanted to create a generic function that receive a hashref path (just like the build-in exists function do) then test if the entry exists (using exists) then do some more tests on the object if it exists. I am able to do it with a workaround, it's just that I wanted to be fancy and be able to send only on parameter to my function, instead of two, like I am doing now.

I hope this explanation is clear enough. I cannot get into more details and I don't want to start a "why-don't-you-do-this-instead" thread, I just wanted to know if it was possible to emulate the exists function.

Thanks very much for your reply!

There are no stupid questions, but there are a lot of inquisitive idiots.

-- greengaroo

Comment on Re^2: How can I re-program the exists function?

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Re^3: How can I re-program the exists function? (false) by tye (Sage) on Aug 27, 2012 at 16:47 UTC
my goal is to test an entry from a hashref, these entries contains objects A reference to an object can't be undef() or even false (unless you do some strange overloading) so what you want is trivial: `mytest( $hash{object} \|\| '' ); sub mytest { my( $obj ) = @_; return if ! $obj; }` [download] The "`\|\| ''`" is there just to ensure that autovivification doesn't happen. I believe current versions of Perl actually avoid autovivification for this case if you don't assign to `$_[0]` in the mytest sub, but that's the kind of detail that is subject to change so I tend to "play it safe" on such issues. - tye	[reply] [d/l] [select]

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Re^3: How can I re-program the exists function? (false)
by tye (Sage) on Aug 27, 2012 at 16:47 UTC

my goal is to test an entry from a hashref, these entries contains objects

A reference to an object can't be undef() or even false (unless you do some strange overloading) so what you want is trivial:

    mytest( $hash{object} || '' );

sub mytest {
    my( $obj ) = @_;
    return
        if  ! $obj;
}
[download]

The "|| ''" is there just to ensure that autovivification doesn't happen. I believe current versions of Perl actually avoid autovivification for this case if you don't assign to $_[0] in the mytest sub, but that's the kind of detail that is subject to change so I tend to "play it safe" on such issues.

- tye

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