[calopetreep]

Do you mean you have trouble with seeing what's going on inside a long function composition? I wrote a cool function to examine it with almost no code changes:

  module TraceCompose where

  import Debug.Trace

  -- | Trace a value, resulting in the value itself
  idTrace :: Show a => a -> a
  idTrace x = trace (show x) x

  traceCompose :: (Show a, Show b, Show c) =>
    (b -> c) -> (a -> b) -> a -> c
  traceCompose f g = h f . h g . h id
    where h f x = idTrace (f $ seq x x)

  -- Replace "normal" function composition using traceCompose.
  test = (+1) . (*10) $ 4
    where (.) = traceCompose

When you run "test", it will print:

4 40 41

(i.e., the outputs of each function at each point in the composition in order of execution.)