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Strange bevahiour of grep function.

by kmxillo (Initiate)
on May 14, 2013 at 15:33 UTC ( #1033508=perlquestion: print w/replies, xml ) Need Help??
kmxillo has asked for the wisdom of the Perl Monks concerning the following question:

I have two arrays of hashes (@r_objects and @r_objects). A want to find the value in @A that differs from @B. Using grep function with the condition 'eq' works fine. My problem is when I use 'ne', it shows all $_obj_prevVal from @prev_values. Here is my code.

my @_remainObj = map { my $_obj_prevVal = $_->{OBJECT}; my $_mnum_prevVal = $_->{METRIC}; my $_notObj_rObjects = grep { $_obj_prevVal ne $_->{OBJECT} and +$_mnum_prevVal eq "1"} @r_objects; $_notObj_rObjects ? $_obj_prevVal : (); } @prev_values;
Does anyone can help me? Thank you

Replies are listed 'Best First'.
Re: Strange bevahiour of grep function.
by LanX (Chancellor) on May 14, 2013 at 15:57 UTC
    Hard to read, but if you want to invert a logical clause you also have to switch and to or and invert all sub-clauses.

    see De_Morgan's_laws

    And consider to use List::MoreUtils 'any' instead of grep.

    HTH =)

    Cheers Rolf

    ( addicted to the Perl Programming Language)


    s/ List::Util / List::MoreUtils /

Re: Strange bevahiour of grep function.
by RichardK (Parson) on May 14, 2013 at 16:55 UTC

    You don't need the test of $_mnum_prevVal in the grep as it never changes (it doesn't refer to $_), so you can move that outside the grep and that might make things easier.

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