Reversing binary numbers in Haskell

Question

I have defined data type for Binary numbers as follows

data Bin = Nil | O Bin | I Bin 
           deriving (Show, Eq)

i want to define a function reverse :: Bin -> Bin so that when i give input like

reverse (I (O (I (I Nil)))) i should get the outut I (I (O (I Nil))) that means reversed as input, any body please give me hint how i can do this ?

Answer 1

Why are you doing this this way? Why not something like this:

data Bit = I | O
newtype Bin = List Bit

Then you could just use the Prelude's reverse operation directly...

Edit A simple substitution from the Prelude's function:

reverse x = rev x []
  where
    rev [] a = a
    rev (x:xs) a = rev xs (x:a)

yields:

reverse x = rev x Nil
  where
    rev Nil a = a
    rev (I xs) a = rev xs (I a)
    rev (O xs) a = rev xs (O a)

The thing is, your type is very similar to the list type:

data List a = a : (List a) | []

so the logic for the List routines applies directly to your type.