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Vigenère cipher: Difference between revisions
→{{header|Scala}}
Line 2,425:
Deciphered: ATTACKAT0620.
</pre>
===Alternate Scala implementation===
This version first creates a sequence of characters from A to Z and a "flattened" Vigenere Square. It then encodes or decodes by just indexing between these two sequences.
The code does no error checking and assumes that a valid key of 25 characters or less in length is passed to it.
Also, it will only encode or decode upper case characters in the range A to Z passing any other character through unchanged.
<lang scala>class Vigenere(val key: String) {
private def rotate(p: Int, s: IndexedSeq[Char]) = s.drop(p) ++ s.take(p)
private val chars = 'A' to 'Z'
private val vSquare = (chars ++
rotate(1, chars) ++
rotate(2, chars) ++
rotate(3, chars) ++
rotate(4, chars) ++
rotate(5, chars) ++
rotate(6, chars) ++
rotate(7, chars) ++
rotate(8, chars) ++
rotate(9, chars) ++
rotate(10, chars) ++
rotate(11, chars) ++
rotate(12, chars) ++
rotate(13, chars) ++
rotate(14, chars) ++
rotate(15, chars) ++
rotate(16, chars) ++
rotate(17, chars) ++
rotate(18, chars) ++
rotate(19, chars) ++
rotate(20, chars) ++
rotate(21, chars) ++
rotate(22, chars) ++
rotate(23, chars) ++
rotate(24, chars) ++
rotate(25, chars))
private var encIndex = -1
private var decIndex = -1
def encode(c: Char) = {
encIndex += 1
if (encIndex == key.length) encIndex = 0
if (chars.contains(c)) vSquare((c - 'A') * 26 + key(encIndex) - 'A') else c
}
def decode(c: Char) = {
decIndex += 1
if (decIndex == key.length) decIndex = 0
if (chars.contains(c)) {
val baseIndex = (key(decIndex) - 'A') * 26
val nextIndex = vSquare.indexOf(c, baseIndex)
chars(nextIndex - baseIndex)
} else c
}
}</lang>
<lang scala>val text = "ATTACKATDAWN"
val myVigenere = new Vigenere("LEMON")
val encoded = text.map(c => myVigenere.encode(c))
println("Plaintext => " + text)
println("Ciphertext => " + encoded)
println("Decrypted => " + encoded.map(c => myVigenere.decode(c)))</lang>
Output
<pre>Plaintext => ATTACKATDAWN
Ciphertext => LXFOPVEFRNHR
Decrypted => ATTACKATDAWN</pre>
=={{header|Seed7}}==
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