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Postings from April 2010
Harry Putnam wrote:
>
> I posted my effort at digging out the matches.
>
> I see the way you did it, even though not the exact results I was
> after is 100s of percent better way to write it.
>
> I'm curious though if the overhead is different in your compact code
> compared to mine. That is, if all that spinning through dir2:
> ,----
> | my ($r1full,$r1end);
> | while (($r1full,$r1end) = each(%r1h)) {
> | foreach my $key (keys %r2h) {
> `----
>
> is more costly than your compact example:
>
> ,----
> | if ( exists $r2h{ $rlend } ) {
> | print "$r2h{$rlend} MATCHES $r1end\n";
> `----
Yes.
> In other words is the perl interpreter working harder in one case?
Yes.
> [...]
>
> cat ex1.pl
> #!/usr/local/bin/perl
>
> use strict;
> use warnings;
> use File::Find;
> use Cwd;
>
> my $topdir2recurse = shift;
>
> ## Trying to use JKs' notation
>
> my $cnt1 = 0;
> find sub {
> if(-f $File::Find::name){
> $cnt1++;
> }
> },$topdir2recurse;
>
> print "Finished 1st recurse, count was <$cnt1>\n";
> # ------- ------- ---=--- ------- -------
> my $cnt2 = 0;
> find sub {
> my $dir = getcwd;
> if(-f $dir . '/' . $_){
> $cnt2++;
> }
> },$topdir2recurse;
>
> print "Finished 2nd recurse, count was <$cnt2>\n";
>
> __END__
> ------- --------- ---=--- --------- --------
> run ex1.pl ./dir1
> Finished 1st recurse, count was <0>
> Finished 2nd recurse, count was <625>
> ------- --------- ---=--- --------- --------
> I'm sure my test is invalid since you've shown that $File::Find:;dir
> is all I needed. But not sure I see why it works in one case but not
> this case. (Something wrong with the example no doubt)
You need to do the -f file test on $_ instead of either
$File::Find::name or getcwd() . '/' . $_ because *you* *are* *using*
*relative* *paths* instead of absolute paths. File::Find::find()
already changes your location to $File::Find::dir so $_ is *in* *the*
*current* *directory* and there is no need to prepend anything to $_ to
use a file test on it. Trying to use a file test on $File::Find::name
searches for the file name *relative* to the current directory.
> [...] script snipped
>
> Yes, once I get it working... and figure out what is actually going on
> in that compact code it is the kind of code I'd like to be able to
> dash off (and read) some day.
>
> I don't see (yet) what is supposed to be happening here. There is a
> lot happening that isn't obvious to me.
>
> $data{ $_ }{ $r2 }++
> $data{ $_ } .. (ok thats what I called the end name)
>
> Are {} playing the role of rgx delimiters in `{ $r2 }'
What are "rgx" delimiters?
> Or is it the same as saying:
> $data{ $_ } eq $r2
No.
> I'm not sure what roll the `++' plays there either.
That is incrementing the value in $data{ $_ }{ $r2 }.
John
--
The programmer is fighting against the two most
destructive forces in the universe: entropy and
human stupidity. -- Damian Conway
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