-- returns a list of the last elements of the lists in a list of lists
lasts :: [[a]] -> [a]
lasts [] = []
lasts [[a]] = [a]
lasts [[a,b]] = [b]
lasts [[a,b,c]] = [c]
lasts [[b],[a]] = [b,a]
lasts [[c],[a,b]] = [c,b]
lasts [[a,b],[c,d]] = [b,d]
lasts [[c,d],[b]] = [d,b]
lasts [[c],[d,e],[f]] = [c,e,f]
lasts [[c,d],[e,f],[g]] = [d,f,g]