[Haskell-beginners] Evaluation oddity

[Torsten Otto]

Hi all,

maybe one of you sees a difference, I sure don’t… The full code for this is below.

When I call 

*Main> diffieH 23 16 20
13

and use the result in

*Main> encipher "abc" 13
„nop"

I get the letters to be expected. However, when I combine these into

> start text p a b = encipher text (diffieH p a b)

*Main> start "abc" 23 16 20
„efg"

the result changes. 

Any hints are most welcome. 

Thank you and regards
Torsten







> import Data.Char

> diffieH p a b = (b ^ a) `mod` p

> number2letter number = chr (number + 96)
> letter2number letter = (ord letter) - 96

> start text p a b = encipher text (diffieH p a b)

> encipher []       _          = []
> encipher (b:rest) key   = (number2letter (((letter2number b)+key) `mod` 26)) : (encipher rest key)