Question

Complete Haskell newbie here, my apologies….

I am trying to create a sequence of values out of another sequence and the last value generated (So it’s not completely obvious to me how I would use map).

In clojure I would use a loop construct which is basically equivalent to a recursive function. So I thought I could use this problem with a recursive function along the lines of

genSequence :: [a] -> [b] -> [a]
genSequence result [] = reverse result
genSequence a:as b:bs = genSequence ((computeNextA a b):a:as) bs

and I guess this isn’t so bad (the real function is of course more complicated …) but I read about monads (read the excellent tutorial by Philip Walder, then some stuff on monads in clojure) and can’t help the feeling that I should be using them here. So far my knowledge of monads is purely theoretical, unfortunately, so I would be very thankful if you could help me along.

Answer 1

Not sure if this helps, but something like (assuming that computeNextA is +)

genSequence [4] [60,70,80,90]
--[4,64,134,214,304]

is equivalent to

scanl (+) 4 [60,70,80,90]
--[4,64,134,214,304]