atbashChar :: Char -> Char
atbashChar c
    | isLetter c = symmetric
    | otherwise  = c
  where
    lc = toLower c
    symmetric = toEnum $ fromEnum 'a'
                       + fromEnum 'z'
                       - fromEnum lc
atbashChar :: Char -> Char
atbashChar c
    | isLetter c = symmetric
    | otherwise  = c
  where
    lc = toLower c
    symmetric = toEnum $ fromEnum 'a'
                       + fromEnum 'z'
                       - fromEnum lc
atbashChar c
    | isLetter c = symmetric
    | otherwise  = c
  where
    lc = toLower c
    symmetric = toEnum $ fromEnum 'a'
                       + fromEnum 'z'
                       - fromEnum lc