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Postings from May 2008
Richard Lee wrote:
> Gunnar Hjalmarsson wrote:
>> Richard Lee wrote:
>>>
>>> ------------ code of Gunnar's ----------------
>>>
>>> my $numbers_wanted = 2;
>>> my ( @datawanted, @numbers );
>>>
>>> LOOP: foreach ( @datas ) {
>>> my @test = split;
>>> foreach my $num ( @numbers ) {
>>> next LOOP if grep( $num->{$_}, @test ) >= $numbers_wanted;
>>> }
>>> push @datawanted, $_;
>>> push @numbers, { map { $_ => 1 } @test };
>>> }
>>>
>>> print "$_\n" for @datawanted;
>>
>> It iterates over @datas and stores some of the elements in @datawanted
>> based on (my interpretation of) the OP's criteria. There is nothing
>> mysterious with the code; everything can be looked up in the Perl docs.
>>
>> @numbers is a help variable where the numbers in previously stored
>> elements are made conveniently accessible for lookups. The expression
>>
>> map { $_ => 1 } @test
>>
>> creates a key/value list where the elements of @test are the keys (see
>> "perldoc -f map"), and
>>
>> push @numbers, { map { $_ => 1 } @test };
>>
>> makes the list an anonymous hash and adds a reference to that hash to
>> @numbers.
>>
>> grep() is used in scalar context to compare the elements with
>> previously stored elements and test against the OP's criteria.
>>
>> perldoc -f grep
>
> why does program go over empty array at the begining?
>
> foreach my $num ( @numbers ) {
> next LOOP if grep( $num->{$_}, @test ) >= $numbers_wanted;
> }
Since @numbers is empty at the first iteration of the outer loop, the
program skips the inner loop. So what?
I simply posted some code that gives the desired result. Please feel
free to criticize the code or post an alternative solution, but I don't
see the point with asking "why" with respect to a piece of code out of
context.
--
Gunnar Hjalmarsson
Email: http://www.gunnar.cc/cgi-bin/contact.pl
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