On Sun, 10 Apr 2011 18:49:59 +0200, Anwar Bari
HI Cafe I have to make a function to check that I have one occurrence of the last element (z) of the same list [a,b] in the tuple
[([a,b],z)] For example [([1,2],3),([1,1],5),([1,3],6).......] this is true because there is one single z for each single list.
while this one is false [([1,2],3),([1,2],5),([1,3],6).......] because 3&5 were found for the same list [1,2]
import Data.Function (on) import Data.List (groupBy, nub, sort) a = [([1,2],3),([1,1],5),([1,3],6)] b = [([1,2],3),([1,2],5),([1,3],6)] check = all ((< 2) . length . nub) . groupBy ((==) `on` fst) . sort main = print $ check a && not (check b) I don't know if I interpreted your specifications correctly; this program ignores identical tuples, so check [([1,2],3), ([1,2],3), ([1,3],6)] returns True; if this is not what you meant, remove the " . nub" from the program. Regards, Henk-Jan van Tuyl -- http://Van.Tuyl.eu/ http://members.chello.nl/hjgtuyl/tourdemonad.html --