Vigenère cipher: Difference between revisions

=={{header|OCaml}}==

<lang ocaml>let cipher src key crypt =

let str = String.uppercase src in

let key = String.uppercase key in

(* strip out non-letters *)

let len = String.length str in

let rec aux i j =

if j >= len then String.sub str 0 i else

if str.[j] >= 'A' && str.[j] <= 'Z'

then (str.[i] <- str.[j]; aux (succ i) (succ j))

else aux i (succ j)

in

let res = aux 0 0 in

let slen = String.length res in

let klen = String.length key in

let d = int_of_char in

let f =

if crypt

then fun i -> d res.[i] - d 'A' + d key.[i mod klen] - d 'A'

else fun i -> d res.[i] - d key.[i mod klen] + 26

in

for i = 0 to pred slen do

res.[i] <- char_of_int (d 'A' + (f i) mod 26)

done;

(res)

let () =

let str = "Beware the Jabberwock, my son! The jaws that bite, \

the claws that catch!" in

let key = "VIGENERECIPHER" in

let cod = cipher str key true in

let dec = cipher cod key false in

Printf.printf "Text: %s\n" str;

Printf.printf "key: %s\n" key;

Printf.printf "Code: %s\n" cod;

Printf.printf "Back: %s\n" dec;

;;</lang>

Run:

<pre>$ ocaml vigenere_cipher.ml

Text: Beware the Jabberwock, my son! The jaws that bite, the claws that catch!

key: VIGENERECIPHER

Code: WMCEEIKLGRPIFVMEUGXQPWQVIOIAVEYXUEKFKBTALVXTGAFXYEVKPAGY

Back: BEWARETHEJABBERWOCKMYSONTHEJAWSTHATBITETHECLAWSTHATCATCH</pre>