Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!cornell!rochester!rutgers!att!ihlpl!canoura
From: canoura@ihlpl.ATT.COM (jlcanoura)
Newsgroups: comp.lang.lisp
Subject: lisp problem
Keywords: help
Message-ID: <10053@ihlpl.ATT.COM>
Date: 10 Apr 89 23:57:11 GMT
Organization: AT&T Bell Laboratories - Naperville, Illinois
Lines: 27

PLEASE, does anybody know how to solve this problem in LISP.

By using recursion and the Append function, Given a list of
nondistinct elements and a positive number K where K is <=
the size of the list, I need to write a function which returns
a list, the element of whose are the combinations of the 
element of the given list taken K at a time. 
e.g.(COMB '(n1 n2 ....n) K)

Examples. ( COMB is the name of the function)

(COMB '(1 2 3 ) 2) should return  
  ((1 2) (1 3) (2 3))

(COMB '(1 2 3) 3) should return
  ((1 2 3))

(COMB '(1 2 3) 1) should return
  ((1) (2) (3))

etc.


any help will be apreciated.


                                           ihlpl!canoura