Re: [Haskell-beginners] How to select items from one list depending on another

2010/11/10 C K Kashyap :

Hi, I have this problem at hand -

Given two lists

list1 = [0,1,2,0,1,4]

list2 = [1,2,3,4,5,6]

I need to take items from the second list only when the corresponding item in list1 is non-zero.

list3 = map snd $ filter takeValid $ zip list1 list2 where                       takeValid (a,b) = a /= 0

Is there a shorter way?

You can use list comprehenison and pattern matching here: list3 = [xs | (0, xs) <- zip list1 list2]