[Haskell-cafe] Code review: list-like datatype with constant time appending based on function composition.

[Arie Peterson]

> What about my doubts on why it works so lazily?

Suppose 'f' is the function '(1 :)', and 'g' is some other unspecified other 
function of type '[Integer] -> [Integer]' ("difference list").

You may evaluate the concatenation '(f . g) []' like this:

(f . g) []
  = f (g [])
  = 1 : g []

and at this point, you already have partial knowledge of the resulting list.

Note that we use "lazy evaluation", in the sense that we do not evaluate the 
argument 'g []' to the function 'f' right away, but proceed by first 
substituting the definition of 'f'.