Re: How to replace greedy alternation?

It can be done with one regexp.

/^(?=.*a)(?=.*b)(?=.*c).*d/
   or die;
[download]

If you want to know the order in which they came,

my %order;
@order{qw( a b c d )} =
      map length, /^(?=(.*?)a)(?=(.*?)b)(?=(.*?)c)(.*?)d/
   or die;

my @ordered = sort { $order{$a} <=> $order{$b} } keys %order;
[download]

This is probably slow for long strings.

Update: Actually, no need for a hash.

my @order = map length, /^(?=(.*?)a)(?=(.*?)b)(?=(.*?)c)(.*?)d/
   or die;

my @ordered = ( qw( a b c d ) )[
   sort { $order[$a] <=> $order[$b] } 0..$#order
];
[download]

Update: Back to the practical, using multiple regexp and saving @- should be much faster. Especially if scanning for constants.

my @unordered = qw( a b c d );

my @order;
for my $s (@unordered) {
   push @order, /\Q$s/ ? $-[0] : die;
}

my @ordered = @unordered[
   sort { $order[$a] <=> $order[$b] } 0..$#order
];
[download]

Comment on Re: How to replace greedy alternation? Select or Download Code

Replies are listed 'Best First'.
Re^2: How to replace greedy alternation? by jwkrahn (Abbot) on Jan 28, 2009 at 06:52 UTC
Another way to do it: `my %order; /(?=.(a))(?=.(b))(?=.*(c))/ and @order{ qw/a b c/ } = @-[ 1 .. $#- ] +;` [download]	[reply] [d/l]
Re^2: How to replace greedy alternation? by Anonymous Monk on Jan 28, 2009 at 07:17 UTC
This code does not work: `/^(?=.a)(?=.b)(?=.c).d/` [download] For example, when used in the code below nothing s returned. `echo bacd\| perl -ne '/^(?=.a)(?=.b)(?=.c).d/; print "$1 $2 $3\n";'` [download]	[reply] [d/l] [select]
Re^3: How to replace greedy alternation? by jwkrahn (Abbot) on Jan 28, 2009 at 07:25 UTC
That is because there are no capturing parentheses in your regular expression and so `$1`, `$2` and `$3` are not affected and thus contain nothing.	[reply] [d/l] [select]