warnings and grep problem

jeanluca has asked for the wisdom of the Perl Monks concerning the following question:

Replies are listed 'Best First'.
Re: warnings and grep problem by Fletch (Bishop) on Jun 20, 2006 at 15:23 UTC
Something doesn't quite . . . match up. Calling grep on `%$packlist` rather than (say) `keys %$packlist` seems odd. Not to mention you seem to be trying to use `grep` in one step where you probably want a map of `grep`'d results. Modifying things inside of a `grep` is . . . unusual; `grep` is for selecting items from a list which satisfy some predicate, `map` is for constructing a new list by applying some transformation to the elements of an existing list. Those things aside, I'd use FIle::Basename to split the paths apart instead of a regex.	[reply] [d/l] [select]
Re^2: warnings and grep problem by jeanluca (Deacon) on Jun 20, 2006 at 15:49 UTC
You're probably right (I'm still not very good with grep and map) Anyway I tried the following `my $hash = map { /\Q$dir\E(\w+?)\.pm$/ and defined $1, $1 } keys %$pac +klist ;` [download] Looks a lot better,but printing it like `foreach ( keys %hash) print $_ ; }` [download] gives a new warning `Odd number of elements in hash assignment at /usr/lib/p....` [download] Any suggestions ? LuCa	[reply] [d/l] [select]
Re^3: warnings and grep problem by Fletch (Bishop) on Jun 20, 2006 at 16:10 UTC
You're attempting to use the number of keys ~~which matched~~ to initialize a hash. Trying to use a single scalar to initialize a hash isn't going to produce anything useful. `my @desired_keys = grep { /\Q$dir\E.?\.pm$/ } keys %$packlist; my %hash; @hash{ map { /\Q$dir\E(\w+?)\.pm$/; $1 } @desired_keys } = @desired_ke +ys;` [download] Update:* Gah. Me no write well. Reworded to (hopefully) clarify.	[reply] [d/l]
Re^4: warnings and grep problem by jeanluca (Deacon) on Jun 20, 2006 at 16:36 UTC
Re^3: warnings and grep problem by eric256 (Parson) on Jun 20, 2006 at 16:11 UTC
You assigned the output of the map to a scalar $has so you'll just get the number of elements map returned, not the actual elements. Then you did keys %hash which is a whole new variable. The following might do what you want, but if you are messing with path/file names then i would highly recommend use a CPAN module. `my @dirs = map { s/\Q$dir\E(\w+?)\.pm$/$1/ } keys %$packlist; for (@dirs) { print $_, "\n"; }` [download] ___________ Eric Hodges	[reply] [d/l]
Re: warnings and grep problem by Moron (Curate) on Jun 20, 2006 at 16:14 UTC
The pattern doesn't match for every key and value of the hash, causing $2 to be undefined for such cases. To resolve that alone: `sub _find_modules { my $dir = shift ; my ($inst) = ExtUtils::Installed->new(); my $packlist = $inst->packlist("My_Package"); return grep { /.?\Q$dir\E\w+\.pm$/ and s/(.?\Q$dir\E)(\w+)(\.pm) +$/$2/; } %$packlist ; }` [download] -M Free your mind	[reply] [d/l]
Re: warnings and grep problem by OfficeLinebacker (Chaplain) on Jun 20, 2006 at 14:54 UTC
It's not matching the second regular expression grouping; are you sure the first group isn't being too "greedy?" UPDATE: Also, I may be reading this wrong, but shouldn't there be a g after the regular expression? (meaning you want to do this for all modules, not just the first one) _________________________________________________________________________________ I like computer programming because it's like Legos for the mind.	[reply]
Re^2: warnings and grep problem by jeanluca (Deacon) on Jun 20, 2006 at 15:07 UTC
when use `return grep { s/(\Q$dir\E)(\w+)(\.pm)$/$2/g } %$packlist ; or return grep { s/(\Q$dir\E)(\w+?)(\.pm)$/$2/g } %$packlist ;` [download] gives me the same errors. I think this problem occures when it encounters something like /usr/lib/perl5/site_perl/5.8.7/My_Package/Sub_Package/Some_Module.pm.swp Luca	[reply] [d/l]
Re: warnings and grep problem by Jasper (Chaplain) on Jun 20, 2006 at 16:33 UTC
It's almost certainly to do with running the regex on both the key and the value of the hash. Probably some of the values of a packlist object (returned by ExtUtils::Installed->new->packlist()) are undefined... Is there a function of that packlist that returns what you want, rather than dumping the whole object hash? There's no point in doing `/match/ && s/match/foo/` that's silly. Instead, try something like `defined && s/match/foo/` inside the grep. But know what you want to run the substitution on first (and other people have suggested this, I know) and do it only on those...	[reply] [d/l] [select]