Fixed point combinator in Haskell

Question

The fixed point combinator doesn\'t always produce the right answer given the definition:

fix f = f (fix f)

The following code does not ter

Answer 1

You can't define fix the way you've mentioned since f x may not even be comparable. For instance, consider the example below:

myFix f x | f x == f (f x)  = f x
          | otherwise       = myFix f (f x)

addG f a b =
  if a == 0 then
    b
  else
    f (a - 1) (b + 1)

add = fix addG -- Works as expected.
-- addM = myFix addG (Compile error)