inits +containers

inits :: Seq a -> Seq (Seq a)
containers Data.Sequence
O(n). Returns a sequence of all prefixes of this sequence, shortest first. For example, > inits (fromList "abc") = fromList [fromList "", fromList "a", fromList "ab", fromList "abc"] Evaluating the ith prefix takes O(log(min(i, n-i))), but evaluating every prefix in the sequence takes O(n) due to sharing.