Rotational Cipher

Challenge Overview

Create an implementation of the rotational cipher, also sometimes called the Caesar cipher.

Visit the rotational-cipher exercise on Exercism to read the full instructions and download the exercise files.

Community Solutions

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The following are the top 3 community solutions by stars:

Solution 1 by @glennj (⭐ 0) — View on Exercism
Solution 2 by @hading (⭐ 0) — View on Exercism
Solution 3 by @rammstein (⭐ 0) — View on Exercism

Source: Exercism sml/rotational-cipher

💡 View Solution

fun rotate (shiftKey: int) (text: string): string =
  let val alphabet = explode "abcdefghijklmnopqrstuvwxyz"
      val shift    = shiftKey mod length alphabet
      val rotated  = List.drop (alphabet, shift) @ List.take (alphabet, shift)

      val alphabet = alphabet @ List.map Char.toUpper alphabet
      val rotated  = rotated  @ List.map Char.toUpper rotated
      val mapping  = ListPair.zip (alphabet, rotated)

      fun translate c =