Xah Lee <xah...@gmail.com> writes:
> here's a interesting toy list processing problem. > > I have a list of lists, where each sublist is labelled by > a number. I need to collect together the contents of all sublists > sharing > the same label. So if I have the list > > ((0 a b) (1 c d) (2 e f) (3 g h) (1 i j) (2 k l) (4 m n) (2 o p) (4 q > r) (5 s t)) > > where the first element of each sublist is the label, I need to > produce: > > output: > ((a b) (c d i j) (e f k l o p) (g h) (m n q r) (s t)) > > a Mathematica solution is here: > http://xahlee.org/UnixResource_dir/writ/notations_mma.html > > R5RS Scheme lisp solution: > http://xahlee.org/UnixResource_dir/writ/Sourav_Mukherjee_sourav.work_gmail.scm > by Sourav Mukherjee > > also, a Common Lisp solution can be found here: > http://groups.google.com/group/comp.lang.lisp/browse_frm/thread/5d1ded8824bc750b? It's too complex. Just write: (let ((list '((0 a b) (1 c d) (2 e f) (3 g h) (1 i j) (2 k l) (4 m n) (2 o p) (4 q r) (5 s t)))) (mapcar (lambda (class) (reduce (function append) class :key (function rest))) (com.informatimago.common-lisp.list:equivalence-classes list :key (function first))) ) --> ((S T) (Q R M N) (G H) (O P K L E F) (I J C D) (A B)) -- __Pascal Bourguignon__ http://www.informatimago.com/ -- http://mail.python.org/mailman/listinfo/python-list
