Haskell: Int to Char

Question

I am using the function fromEnum to convert a character to its corresponding ASCII Int. For example:

fromEnum 'A'

returns 65.

Now, assuming I had a function that did:

(fromEnum 'A')+1

And then wanted to convert the returned value (66) to a Char which would be 'B'. What is the best way of doing so?

Thanks!

Answer 1

You can use ord :: Char -> Int and chr :: Int -> Char functions from Data.Char.

> chr (ord 'a' + 1)
'b'

But don't forget to import Data.Char in source file or :m +Data.Char in ghci.

The same thing with fromEnum :: Enum a => a -> Int and toEnum :: Enum a => Int -> a:

toEnum (fromEnum 'a' + 1) :: Char

The last part of this expression says haskell what type we are expecting to help the type system infer right type. But in this case we can drop :: Char:

isLower $ toEnum  (fromEnum 'a' + 1)

because isLower has type Char -> Bool. So it is expecting toEnum (fromEnum 'a' + 1) to be Char.

Anyway, the solution of bheklilr is good enough :) I just wanted to show you few ways of solving your problem.

Answer 2

You can use succ to implement the behavior you want:

nextLetter :: Char -> Char
nextLetter c
    | c == 'Z' = 'A'
    | otherwise = succ c