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=={{header|Julia}}==
{{works with|Julia|01.65}}
<lang Julia>
<lang Julia>function encrypt(msg::AbstractString, key::AbstractString)
→(a::Char, b::Char, ± = +) = 'A'+((a-'A')±(b-'A')+26)%26
msg = uppercase(join(filter(isalpha, collect(msg))))
←(a::Char, b::Char) = →(a,b,-)
key = uppercase(join(filter(isalpha, collect(key))))
msglen = length(msg)
keylen = length(key)
cleanup(str) = filter(a-> a in 'A':'Z', collect(uppercase.(str)))
if keylen < msglen
match_length(word, len) = repeat(word,len)[1:len]
key = repeat(key, div(msglen - keylen, keylen) + 2)[1:msglen]
end
function →(message::String, codeword::String, ↔ = →)
enc = Vector{Char}(msglen)
plaintext = cleanup(message)
@inboundskey for= i in 1:match_length(cleanup(codeword),length(msgplaintext))
return String(plaintext .↔ key)
enc[i] = Char((Int(msg[i]) + Int(key[i]) - 130) % 26 + 65)
end
return join(enc)
end
←(message::String, codeword::String) = →(message,codeword,←)
cyphertext = "I want spearmint gum" → "Gimme!"
function decrypt(enc::AbstractString, key::AbstractString)
println(cyphertext)
enc = uppercase(join(filter(isalpha, collect(enc))))
println(cyphertext ← "Gimme!")
key = uppercase(join(filter(isalpha, collect(key))))
msglen = length(enc)
keylen = length(key)
if keylen < msglen
key = repeat(key, div(msglen - keylen, keylen) + 2)[1:msglen]
end
msg = Vector{Char}(msglen)
@inbounds for i in 1:length(enc)
msg[i] = Char((Int(enc[i]) - Int(key[i]) + 26) % 26 + 65)
end
return join(msg)
end
const messages = ("Attack at dawn.", "Don't attack.", "The war is over.")
const key = "LEMON"
for msg in messages
enc = encrypt(msg, key)
dec = decrypt(enc, key)
println("Original: $msg\n -> encrypted: $enc\n -> decrypted: $dec")
{{out}}
<pre>
<pre>Original: Attack at dawn.
"OEMZXYXQMVSQZFKAU"
-> encrypted: LXFOPVEFRNHR
"IWANTSPEARMINTGUM"
-> decrypted: ATTACKATDAWN
</pre>
Original: Don't attack.
-> encrypted: OSZHNEXMQX
-> decrypted: DONTATTACK
Original: The war is over.
-> encrypted: ELQKNCMECIPV
-> decrypted: THEWARISOVER</pre>
=={{header|Kotlin}}==
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