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Re: most efficient buffer sort

by serf (Chaplain)
on Dec 14, 2005 at 12:15 UTC ( #516593=note: print w/ replies, xml ) Need Help??


in reply to most efficient buffer sort

I have been a bit naughty in assuming that it's OK to use

my ($first, $sort, $second, $tail) = split(/\s+/, $_);
to replace your:
m/^(\w+)\s+(\d+)\s+(\w+)(.*)$/
Because if you have multiple spaces immediately after $second they will be lost - but as you're putting the data into HTML table cells this shouldn't be an issue.

NB: I used split(/\s+/, $_) and not split(' ', $_) because you were matching /^(\w+), which may just have been for efficiency and anchoring, but I don't know that you didn't need to make sure that there was no leading white space on the line in the input file.

I have not used GrandFather's map because I needed to do quite a lot to the elements returned by the sort (the tests on $sort and the sprintf) and it looked like it was going to be messy and possibly difficult trying to fit it all in there.

I like map, but I tend to shy away from using it for more than the most basic usage - I know 95%+ of the people I've ever worked with who have to deal with Perl would not be able to understand how the map worked, but could all unroll a foreach loop if they needed to change the code after I had moved on to my next contract.

use strict; use warnings; my $buffer; my $input = "input.dat"; my %colour = ( 'lt_90' => '#00FF00', 'lt_180' => '#FF6600', 'gt_179' => '#FF0000' ); my @lines; open( INPF, $input ) or die "Can't read '$input': $!\n"; while (<INPF>) { my ($first, $sort, $second, $tail) = split(/\s+/, $_); if ( defined $tail && $sort =~ /^\d+$/ ) { push(@lines, [$first, $sort, $second, $tail]); } else { # die "Unable to match any lines: $!\n"; # Do you really want to die with $! here? # There wasn't an error, just a failed test, # so $! won't have a relevant message in it. # (I get "Bad file descriptor" YMMV on your OS?) # Perhaps you want something like: chomp(); die "line: '$_' does not match input format\n"; } } close (INPF); for my $line ( sort { $a->[1] <=> $b->[1] } @lines ) { my ($first, $sort, $second, $tail) = @{$line}; my $colour = "gt_179"; if ( $sort < 90 ) { $colour = "lt_90"; } elsif ( $sort < 180 ) { $colour = "lt_180"; } $buffer .= sprintf ( "<tr bgcolor='%s'><td>%s</td><td>%s</td><td>%s</td><td>%s</td> +</tr>\n", $colour{$colour}, $first, $sort, $second, $tail); } print "$buffer";


Comment on Re: most efficient buffer sort
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Re^2: most efficient buffer sort
by Anonymous Monk on Dec 14, 2005 at 12:36 UTC
    Good point re the die statement. It's just habit to put that line in. I've changed it accordingly. Thanks.
Re^2: most efficient buffer sort
by salva (Abbot) on Dec 14, 2005 at 13:06 UTC
    I like map...

    calling die from inside a map block is not a very good idea, it can hit a bug on the perl interpreter that has only recently being corrected:

    for (1) { map { die } 2 }

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