Check If 2 Arrays Match

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

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Re: Quick Question? by jrsimmon (Hermit) on Jul 21, 2009 at 02:55 UTC
Not tested, but fairly straightforward. This assumes that the exact string represented by $ID shows up somewhere within the filename that you want to match. `use strict; use warnings; chomp(@ID); foreach my $ID(@ID) { foreach my $file (@files){ if ($ID=~ /$file/) { print "$file\n"; #if the matches are unique, you can bail this foreach after a ma +tch last; } } }` [download]	[reply] [d/l]
Re: Quick Question? by toolic (Bishop) on Jul 21, 2009 at 03:03 UTC
quick answer... one way to do it is to use 2 for loops: `use warnings; use strict; my @ids = 0..5; my @files = 3..8; for my $id (@ids) { for my $file (@files) { print "$file\n" if $id eq $file; } } __END__ 3 4 5` [download] Feel free to change the title of your node to something more useful like: "Check if 2 arrays match".	[reply] [d/l]
Re: Quick Question? by halfcountplus (Hermit) on Jul 21, 2009 at 03:02 UTC
Maybe you want something more like this `#!/usr/bin/perl -w use strict; my @ray = qw(one two three); my @two = qw(two next four); foreach my $x (@ray) { foreach my $y (@two) { print $x if ($x eq $y); } }` [download] If you just use @two in the regex match, it will expand to the entire array, ie, you are asking if the filename matches the entire list of filenames, not one of them. Eg. `if ($ID=~ m/one.txt two.txt three.txt/)` [download] which no file will have that name. In this situation methinks it matters not so much, but "eq" will only match exactly, whereas =~ will match if the pattern is a substring.	[reply] [d/l] [select]
Re: Check If 2 Arrays Match by bichonfrise74 (Vicar) on Jul 21, 2009 at 03:50 UTC
Another possible solution? `#!/usr/bin/perl use strict; my @ids = 0..5; my @files = 3..8; my %record; $record{$_}++ for (@ids, @files); print map { "Same file and id: $_\n" if $record{$_} > 1 } %record;` [download]	[reply] [d/l]
Re: Check If 2 Arrays Match by johngg (Canon) on Jul 21, 2009 at 11:23 UTC
... with filenames that are based on those numbers. If the derivation of filename from ID is predictable, it might be more efficient to create a hash of filenames from the IDs then use grep to select appropriate files from your `@files` array rather than keep looping over files and IDs. `use strict; use warnings; my @IDs = qw{ pj7023 ge4872 dr90324 jc824 }; my @files = qw{ XYZ_dr90324.txt XYZ_at728.txt XYZ_jc824.txt XYZ_uf72082.txt XYZ_tc43.txt XYZ_pj7023.txt XYZ_yj82195.txt XYZ_fw607.txt }; my %IDnames = map { my $key = q{XYZ_} . $_ . q{.txt}; $key => 1 } @IDs; my @selectedFiles = grep exists $IDnames{ $_ }, @files; print qq{$_\n} for @selectedFiles;` [download] The output. `XYZ_dr90324.txt XYZ_jc824.txt XYZ_pj7023.txt` [download] It might be that the filename can't be confidently derived from the ID and this method will not work but I thought I'd post the idea just in case. Cheers, JohnGG	[reply] [d/l] [select]
Re: Check If 2 Arrays Match by facedag (Initiate) on Jul 21, 2009 at 04:02 UTC
Thank you for all of the responses, this did the trick: `chomp (@ID); foreach $ID(@ID){ foreach $file(@files){ print "$file" if ($file =~ /($ID)/); } }` [download]	[reply] [d/l]
Re^2: Check If 2 Arrays Match by ELISHEVA (Prior) on Jul 21, 2009 at 08:52 UTC
Unless your ids are always exactly the same length, you might want to replace `/($ID)/` with `/^$ID$/`. Otherwise "123" will match all of the following files: "123", "1234", and "4123". I also omitted the parentheses around `$ID`. "(...)" makes Perl do extra work to "capture" whatever is between the parenthesis. Since you already have the value of `$ID` you don't need to capture it. Another potential bug. If your id contains fullstops, i.e. '.' or other special regular expresssion characters you should probably escape the id, i.e. `/^\Q$ID\E$/`. The reason is that Perl will read the dot as a wildcard, so "1.2" will match "1.2", "122", "152", and so on. Best, beth	[reply] [d/l] [select]
Re^2: Check If 2 Arrays Match by gulden (Monk) on Jul 21, 2009 at 11:04 UTC
One more: `foreach my $id(@ID){ print "$id\n" if grep(/^$id$/, @files); }` [download] ŤA contentious debate is always associated with a lack of valid arguments.ť	[reply] [d/l]