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Re: Sorting large sets of geometric coordinates

by ikegami (Pope)
on Apr 19, 2006 at 20:55 UTC ( #544436=note: print w/ replies, xml ) Need Help??


in reply to Sorting large sets of geometric coordinates

A hash isn't appropriate, because nothing is guaranteed to be unique (as far as you've let on). You also ask to sort, and hashes are unordered.

my @unsorted_data; while (<DATA>) { my @fields = /([\d.]+)/g or next; push(@unsorted_data, \@fields); } my @sorted_data = sort { $a->[1] <=> $b->[1] || $a->[0] <=> $b->[0] } @unsorted_data; print("(($_->[0] $_->[1]) ($_->[2] $_->[3]))\n") foreach @sorted_data;

Update: Tested. Fixed the print.

Update: Fixed the error discussed below.


Comment on Re: Sorting large sets of geometric coordinates
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Re^2: Sorting large sets of geometric coordinates
by thor (Priest) on Apr 20, 2006 at 02:43 UTC
    my @sorted_data = sort { $a->[1] <=> $b->[1] || $a->[0] <=> $a->[0] } @unsorted_data;
    Wouldn't the second part of that sort be a no-op?

    thor

    The only easy day was yesterday

      It handles ties in $row_ly. <=> returns 0 if the two things it compares are equal. For example, if the compare function were to be called to compare the following two rows,
      ((5.0 0.4) (48.0 0.5)) ((48.1 0.4) (99.0 0.5))
      The first <=> would return 0 since $a->[1] (0.4) and $b->[1] (0.4) are both equal. It would then go on to compare $a->[0] (5.0) with $b->[0] (48.1)

      Update: OOPS! Copy and paste error. The code should read:

      my @sorted_data = sort { $a->[1] <=> $b->[1] || $a->[0] <=> $b->[0] } @unsorted_data;

      Nod to BrowserUk for the head's up.

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