Removing prepending “0” output from Haskell toBinary function that converts number to binary string?

Question

I am new to Haskell. My function is supposed to take an integer and convert it to a string in base 2. My code works correctly, but I would like to remove "0" from my results.

For example, toBinary 16 outputs "010000" rather than "10000", as I would like.

Does anyone have any advice?

toBinary :: Integer -> [Char]

toBinary x = if (x == 0) then "0" else toBinary ( div x 2 ) ++ show(mod x 2 )

question from:https://stackoverflow.com/questions/65906539/removing-prepending-0-output-from-haskell-tobinary-function-that-converts-numb

Answer 1

You need a helper function that calls your recursive function, as there's only one case in which you want to prepend "0" (when the number is 0).

toBinary' :: Integer -> String
toBinary' 0 = ""
toBinary' x = toBinary' (div x 2) ++ show (mod x 2)

toBinary :: Integer -> String
toBinary 0 = "0"
toBinary x = toBinary' x