Caesar.fold

-- F#
-- http://www.rosettacode.org/wiki/Caesar_cipher#F.23
module caesar =
  open System

  let cipher n s =
    let shift c =
      if Char.IsLetter c then
        let a = int (if Char.IsLower c then 'a' else 'A')
        char ((int c - a + n) mod 26 + a)
      else c
    String.map shift s

  let encrypt n = cipher n
  let decrypt n = cipher (26 - n)


-- OCaml
module caesar = struct
  open System

  let cipher n s =
    let shift c =
      if Char.IsLetter c then
        let a = int (if Char.IsLower c then 'a' else 'A') in
        char ((int c - a + n) mod 26 + a)
      else c in
    String.map shift s

  let encrypt n = cipher n
  let decrypt n = cipher (26 - n)
end


-- Fold
module Caesar =
  open System

  def cipher n s =
    let shift c =
      if Char.is_letter c then

        a = int (Char.is_lower c ? 'a' : 'A')
        a = int ('a' if Char.is_lower c else 'A')
        a = int (if (Char.is_lower c) 'a' else 'A')
        a = int (if Char.is_lower c then 'a' else 'A')
        a = int (if (Char.is_lower c) 'a' else 'A' end)
        a = int (if Char.is_lower c -> 'a' | else -> 'A')
        a = int (if Char.is_lower c then 'a' else 'A' end)

        char ((int c - a + n) mod 26 + a)
      else
        c
      end
    map shift s

  def encrypt n = cipher n
  def decrypt n = cipher (26 - n)



-- Fold
module Caesar
  open System

  def cipher n s =
    let shift c =
      if Char.is_letter c
        a = int (if Char.is_lower c -> 'a' | else -> 'A')
        char ((int c - a + n) mod 26 + a)
      else
        c
      end in
    map shift s

  def encrypt n = cipher n
  def decrypt n = cipher (26 - n)
end