How to return the next letter in the alphabet of given letter wrapped around in Haskell [closed]

Question

Closed. This question does not meet Stack Overflow guidelines. It is not currently accepting answers.

---

Closed 8 years ago.

• This question appears to be off-topic because it lacks sufficient information to diagnose the problem. Describe your problem in more detail or include a minimal example in the question itself.
• Questions asking for code must demonstrate a minimal understanding of the problem being solved. Include attempted solutions, why they didn't work, and the expected results. See also: Stack Overflow question checklist

Improve this question

I'm trying to implement a function that returns the next letter in alphabetical order. For example:

> returnNext 'A'
  'B'

But also:

> returnNext 'Z'
  'A'

The function should thus cycle between char codes in alphabetical order (mod 26).

Answer 1

Two ways come to mind

import Data.Char
returnNext c = chr (((1 + ord c - ord 'A') `mod` 26) + ord 'A')

Which is kind of ugly to say the least.

And:

returnNext 'Z' = 'A'
returnNext c = chr (ord c + 1)

Both behave differently when not given a letter of the alphabet, but since you didn't specify what should happen in this case I'll assume it's OK.