Let's see, if I execute it by hand:

 

cinits :: [a] -> [[a]]
cinits [] = [[]]
cinits (x:xs) = [] : map (x:) (cinits xs)

 

cinits [1,2,3] = [] : map (1:) ( [] : map (2:) ( [] : map (3:) ( [[]]) ) )

                   = [] : map (1:) ( [] : map (2:) ( [] : map (3:) [[]] ) )

                   = [] : map (1:) ( [] : map (2:) ( [] : [[3]] )

                   = [] : map (1:) ( [] : map (2:) ( [[], [3]] )

                   = [] : map (1:) ( [] : [[2], [2,3]])

                   = [] : map (1:) ( [[], [2], [2,3]])

                   = [[],[1], [1,2], [1,2,3]]

 

Well, I understand this part. But isn't there an easier way to "see" the answer?

 

Thank you for your help!