subsets of a set

*To*: mathgroup at smc.vnet.net*Subject*: [mg70001] subsets of a set*From*: dimmechan at yahoo.com*Date*: Sat, 30 Sep 2006 05:12:23 -0400 (EDT)

In page 226 of John Gray's Mastering Mathematica (unfortunately I had the 1994's edition) there is the following exercise: "Given a finite set (presented as a list) and an integer k find all k-element subsets of the set". There is one solution however for practicing (no there is no professor that asked me this for homeworks! I work individually...) I search for other So considering the following list lst = Tuples[Range[7], 3]; I can erase the sublists containg at least two same elements Cases[lst, {x_, y_, z_} /; x ß? y && x ß? z && y ß? z] but after I cannot erase the permutations of e.g. {1,2,3}; that is in the output there are the sublists {1,2,3}, {2,1,3},{3,1,2} e.t.c. for other triplets. I look for both functional as well pattern matching approaches. Thanks