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Re^3: filtering an array

by philiprbrenan (Monk)
on Sep 01, 2012 at 22:41 UTC ( #991206=note: print w/ replies, xml ) Need Help??

in reply to Re^2: filtering an array
in thread filtering an array

You are using a variable in a pattern matching regular expression and said variable currently has no value. Please try assigning a value to the variable and see what happens. Thanks.

Comment on Re^3: filtering an array
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Re^4: filtering an array
by prbndr (Acolyte) on Sep 01, 2012 at 22:48 UTC

    i see. so if my array @positions is already defined and created, do i need to loop over all the values in @positions and then execute the code you posted?

    something like:

     for (@positions) {@positions = grep $_->[1] =~ /ac/i, @positions;}

    and then:

     for (@positions) {@positions = map $_->[0], @positions;}

      Likewise, the for is unnecessary in this code too:

      for (@positions) {@positions = map $_->[0], @positions;}

      It should just be:

      @positions = map $_->[0], @positions;

      because map iterates over the array you give it. Even better, you could write:

      $_ = $_->[0] for @positions;

      here we are making the for implicit in map explicit.

        perl still has a problem with this:

        @positions = grep $_->[1] =~ /ac/i, @positions;

        with the same error Use of uninitialized value in pattern match (m//)

      You do not need the for becuase grep loops over the array you give it. Please change:

      for (@positions) {@positions = grep $_->[1] =~ /ac/i, @positions;}


      @positions = grep $_->[1] =~ /ac/i, @positions;
        right, but the error still persists. what here isn't defined?

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