Re: how to simplify this script

Gunnar Hjalmarsson wrote:
> Richard Lee wrote:
>> " It should include '1 2 3' because '1 2 3', '1 2 4', '1 2 7', '1 2 8',
>> '1 2 9' = '1 2'(the common number from the list) + anynumber. "
>> as any of them contains 1 and 2 and I don't understand why '1 2 3' was
>> picked.
>
> My interpretation: Because it's the first element of those with 1 and 
> 2 in them. In other words, the order in which the elements appear in 
> @datas is important for the result.
>
>> Also can someone explain to me in detail what Gunnar Hjalmarsson's
>> solution is doing?
>>
>> ------------ 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;
    }



perl -d ./iii

Loading DB routines from perl5db.pl version 1.25
Editor support available.

Enter h or `h h' for help, or `man perldebug' for more help.

main::(./iii:9):        my @datas = (
main::(./iii:10):           '1 2 3',  '1 2 4', '1 2 7',  '1 2 8', '1 2 
9', '1 6 7',
main::(./iii:11):           '1 7 12', '2 6 7', '4 5 10', '4 5 15'
main::(./iii:12):       );
  DB<1> s
main::(./iii:14):         my $numbers_wanted = 2;
  DB<1> x @datas
0  '1 2 3'
1  '1 2 4'
2  '1 2 7'
3  '1 2 8'
4  '1 2 9'
5  '1 6 7'
6  '1 7 12'
7  '2 6 7'
8  '4 5 10'
9  '4 5 15'
  DB<2> s
main::(./iii:15):         my ( @datawanted, @numbers );
  DB<2>
main::(./iii:17):         LOOP: foreach ( @datas ) {
  DB<2> x $_
0  undef
  DB<3> s
main::(./iii:18):             my @test = split;
  DB<3> x $x-^H^H
Unrecognized character \x08 at (eval 
8)[/usr/perl5/5.8.4/lib/perl5db.pl:619] line 2.
        eval '($@, $!, $^E, $,, $/, $\\, $^W) = @saved;package main; $^D 
= $^D | $DB::db_stop;
  $;-

;' called at /usr/perl5/5.8.4/lib/perl5db.pl line 619
        DB::eval called at /usr/perl5/5.8.4/lib/perl5db.pl line 3349
        DB::DB called at ./iii line 18
  DB<4> x $_
0  '1 2 3'
  DB<5> x @test
  empty array
  DB<6> s
main::(./iii:19):             foreach my $num ( @numbers ) {
  DB<6> x @test
0  1
1  2
2  3
  DB<7> x @numbers
  empty array
  DB<8> s
main::(./iii:22):             push @datawanted, $_;
  DB<8> x $num
0  undef
  DB<9> s
main::(./iii:23):             push @numbers, { map { $_ => 1 } @test };
  DB<9> x @numbers
  empty array
  DB<10> x @test
0  1
1  2
2  3
  DB<11> x @_
  empty array
  DB<12> x $_
0  '1 2 3'
  DB<13> s
main::(./iii:23):             push @numbers, { map { $_ => 1 } @test };
  DB<13> x $_
0  1
  DB<14> s
main::(./iii:23):             push @numbers, { map { $_ => 1 } @test };
  DB<14> x $_
0  2
  DB<15> x $_
0  2
  DB<16> s
main::(./iii:23):             push @numbers, { map { $_ => 1 } @test };
  DB<16> x $_
0  3
  DB<17> s
main::(./iii:18):             my @test = split;
  DB<17> s
main::(./iii:19):             foreach my $num ( @numbers ) {
  DB<17> x @numbers
0  HASH(0xc0b04)
   1 => 1
   2 => 1
   3 => 1
  DB<18>