Perl - filtering array elements using grep with multiple conditions

Question

I am trying to filter values in an array using grep (in Perl). My goal is to remove array elements where both the "pending" element is INVALID_APNS and the "token" element is empty

This does not work - it deletes everything. The array contains 0 elements after the rep, but should contain 2.

use constant INVALID_APNS => -1;
@active_connections = (
    {
        pending => INVALID_APNS,
        token=>'123'
    },
    {
        pending => INVALID_APNS,
        token=>'123'
    },
    {
        pending => INVALID_APNS,
        token=>''
    },


);
 @active_connections = grep { ($_->{pending} != INVALID_APNS) && ($_->{token} ne '')} @active_connections;
 print scalar @active_connections;

What am I doing wrong?

ThisSuitIsBlackNot · Accepted Answer · 2017-03-08 22:09:07Z

3

If you want to exclude records with $_->{'pending} == INVALID_APNS && $_->{'token'} eq '', you are negating that improperly to get what grep should include. Either of these should do what you want:

! ( $_->{'pending'} == INVALID_APNS && $_->{'token'} eq '' )

or

$_->{'pending'} != INVALID_APNS || $_->{'token'} ne ''

See https://en.wikipedia.org/wiki/De_Morgan%27s_laws

edited Mar 8, 2017 at 22:09

ThisSuitIsBlackNot

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answered Mar 8, 2017 at 22:02

ysth

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3 Comments

user1361529 Over a year ago

Thanks - I seem to have a brain-freeze at the moment. Your solution works - I don't get why mine is wrong. I'll re-look at this tomorrow morning with some strong coffee and once I get it, I'll mark it as resolved. Thank you!

hobbs Over a year ago

@user1361529 the opposite of "it's big AND it's red" is "it's not big OR it's not red".

user1361529 Over a year ago

Right. I'm an idiot. I can't believe I spent all day on this. Thank you

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