Hello again monks...

Yesterday I received some great advice about sorting in this thread: Sort array according to a value in each element?

Out of the box, the Guttman-Rosler Tranform from BrowserUKdid almost exactly what I needed. (I've been trying to understand the ST and GRT since then.)

I've got the following code which is working fine:

my @sorted = map{
    substr $_, 5;
} 
sort { $b cmp $a } map{
    sprintf '%05d%s',
        $_ =~ m[,\s+(\d+)], $_;
} @msgs;
#SOME STUFF 
foreach my $warning(@sorted) {
    print OUT $warning unless ($warning =~ "<stuff I don't want>"); 
}

[download]


but sprintf reports the following warning on every line of a 7253-line LOG file (line 43 is the "sort..." line):

Use of uninitialized value in sprintf at script.pl line 43, <LOG> line
+ 7253. 
Argument <line from LOG> isn't numeric in sprintf at script.pl line 43
+, <LOG> line 7253

[download]


Oddly enough, this code works just as well:

my @sorted = map{
    substr $_, 125;
} 
sort { $b cmp $a } map{
    sprintf '%0125d%s',
        $_ =~ m[,\s+(\d+)], $_;
} @msgs;

[download]


I just have a feeling that if I could figure out the sprintf/substr interaction, it would be easier to figure out the rest of the code. I'm pretty sure I know what substr is doing here, but I'm not getting the relation to sprintf.

Again, I've got working code, now I'm just trying to make sure I understand why it works.

In reply to What is sprintf doing? by McMahon

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