Preventing duplicate info from being pushed into an array

neo1491 has asked for the wisdom of the Perl Monks concerning the following question:

Dear Monks (apologies for the long title),

My quest for perl enlightenment has once again brought me to the Monastery seeking wisdom.
I'm searching for a way to prevent pushing duplicate information into an array... here's an example:

I'm reading a book looking for three words on the same line... say "perl", "monks", and "rule".
I come across the line "I think Perl Monks Rule". So I use the regular expression below to push that entire line into an array for later use:

  
my @Book = ();
my @MatchFound = ();
foreach (@Book)
  if ( $_ =~ /\bPerl\b/i && /\bMonks\b/i && /\bRule\b/i )
     {
     push @MatchFound, $_;
     }
[download]

On the next page of the book, I run across the same line "I think Perl Monks rule",
but I don't want to push it into the array @MatchFound because it's already there.

How do I scan the array @MatchFound prior to pushing information to it, to determine if that information is already there?

Or, would it be better to wait until I finish the book, then delete all duplicate lines from @MatchFound (which I have no idea how to do either)?

I know there has to be a term for this type of search... something really abstract like unique array identifier or something. Any ideas?

Comment on Preventing duplicate info from being pushed into an array Download Code

Replies are listed 'Best First'.
Re: Preventing duplicate info from being pushed into an array by FunkyMonk (Bishop) on Apr 01, 2008 at 19:07 UTC
You could use something like `my @Book = (); my @MatchFound = (); my %seen; foreach (@Book) { if ( /\bPerl\b/i && /\bMonks\b/i && /\bRule\b/i ) { push @MatchFound, $_ unless $seen{$_}++; } }` [download] Most often, when you're after a unique list in Perl, you want to use a hash	[reply] [d/l] [select]
Re: Preventing duplicate info from being pushed into an array by apl (Monsignor) on Apr 01, 2008 at 19:39 UTC
To slightly simplify what FunkyMonk said, if you're not concerned about preserving the order the matches were found: `my @Book = (); my %MatchFound; foreach (@Book) { $MatchFound{$_}++ if ( /\bPerl\b/i && /\bMonks\b/i && /\bRule\b/i ); }` [download] or even `my @Book = (); my %MatchFound = map{ $MatchFound{$_}++ if ( /\bPerl\b/i && /\bMonks\b +/i && /\bRule\b/i ) } @Book;` [download] Both, alas, are untested...	[reply] [d/l] [select]
Re: Preventing duplicate info from being pushed into an array by wade (Pilgrim) on Apr 01, 2008 at 20:24 UTC
Isn't this why God invented hashes? Instead of: `push @MatchFound, $_;` [download] You can: `%MatchFound{$_} = 1;` [download] You know, with the appropriate declaration and algorithm changes... -- Wade	[reply] [d/l] [select]