Haskell Error Not in scope: data constructor Otherwise

Question

I am trying to create a shift function using let2nat and nat2let functions. This shift function applies a shift factor in the range 0 to 25 to a lower-case letter in the range ’a’ to ’z’. Characters outside this range, such as upper-case letters and punctuation, should be returned unshifted. Make sure your function wraps around at the end of the alphabet.

module Kaan where
import Data.Char

let2nat :: Char -> Int
let2nat x = (ord x) - 97

nat2let :: Int -> Char
m = ['a'..'z']
nat2let x = m !! x

shift :: Int -> Char -> Char
shift x y 
    | (x + let2nat y <= 25) && (x + let2nat y >= 0) = nat2let x + let2nat y
    | (x + let2nat y) > 25 = nat2let (x+let2nat y) `mod` 25
    | Otherwise = y

main = do
     print $ let2nat 'h'

This is what I am getting : Not in scope: data constructor Otherwise`

David Young · Accepted Answer · 2014-10-22 00:20:44Z

5

The binding is named otherwise with a lowercase o. otherwise is defined to be the same as True in the Prelude.

Incidentally, anything (at a value-level) that begins with an uppercase character is a data constructor not a normal binding like otherwise.

answered Oct 22, 2014 at 0:20

David Young

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