Re: [Haskell-beginners] Empty list

Shishir, you need to distinguish between membership (1 is an element of [1,2,3], [] is not) and subsets (both [1] and [] are subsets of [1,2,3]). elem checks the first property, intersection checks the second. On Wed, 25 Mar 2015 10:03 Brandon Allbery wrote:

On Wed, Mar 25, 2015 at 10:00 AM, Norbert Melzer wrote:

...

You are correct, a list is not a set. A list is a list of things, that can be there multiple times. A set is a set of things, where nothing can be twice. So take a look at Data.Set

Note that this won't actually solve the original problem; Haskell is an implementation of a strongly typed lambda calculus, not of number theory, and Haskell collections cannot (easily) contain elements of different types --- so the empty set is not an element of a set, and the empty list is not an element of a list.

-- brandon s allbery kf8nh sine nomine associates allbery.b@gmail.com ballbery@sinenomine.net unix, openafs, kerberos, infrastructure, xmonad http://sinenomine.net _______________________________________________ Beginners mailing list Beginners@haskell.org http://mail.haskell.org/cgi-bin/mailman/listinfo/beginners