Terrence Brannon wrote at Tue, 02 Jul 2002 21:58:51 +0200:
>> A list doesn't stand for any fixed implementation. A list can be regarded as
>> - an array
>
> an array is a standard perl data structure defined as a list with a name. Example:
>
> @A = (1,2,3);
Right. I thought more to the general thinking of lists
(from a computer science/linguistic view).
Allthough what I really thought was the word "Collection".
However, it seems to be more common to me to think,
that a list can represent a set or something else, too.
But perhaps it's better to implement these ideas in a module like
Collection::Compare.
>
> we have a list ( 1, 2, 3) which has a name (@A)
>
>> - a set
>
> hmm, sets can't have repeating elements, right? thus lists are not as restricted wrt
>contents as a
> set.
Year.
Comparing two lists as sets should ignore double elements.
It's like:
my @A; my @B; # both Arrays
my $set_A = Set::Scalar->new(@A); # makes a real set
my $set_B = Set::Scalar->new(@B); # make elements uniq
$set_A->is_eqal($set_B);
what I sometimes would prefer to write:
are_equal_sets( \@A, \@B );
>> - a bag (multiset)
>
> I have forgotten what a bag is. Anyone mind explaining?
>
A bag is a "set" where elements can occur more than one times.
Two bags are equal iff
they have equal elements,
the occurences of each element is the same in both bags.
So a set {1} = {1, 1} = {1, 1, 1} = ...,
while <1> != <1, 1> != <1, 1, 1>.
Greetings,
Janek
