June 2018 Update

Task/Vigen-re-cipher/Factor/vigen-re-cipher.factor

@@ -0,0 +1,30 @@
+USING: arrays ascii formatting kernel math math.functions
+math.order sequences ;
+IN: rosetta-code.vigenere-cipher
+
+: mult-pad ( key input -- x )
+    [ length ] bi@ 2dup < [ swap ] when / ceiling ;
+
+: lengthen-pad ( key input -- rep-key input )
+    [ mult-pad ] 2keep [ <repetition> concat ] dip
+    [ length ] keep [ head ] dip ;
+
+: normalize ( str -- only-upper-letters )
+    >upper [ LETTER? ] filter ;
+
+: vigenere-encrypt ( key input -- ecrypted )
+    [ normalize ] bi@ lengthen-pad
+    [ [ CHAR: A - ] map ] bi@ [ + 26 mod CHAR: A + ] 2map ;
+
+: vigenere-decrypt ( key input -- decrypted )
+    [ normalize ] bi@ lengthen-pad [ [ CHAR: A - ] map ] bi@
+    [ - 26 - abs 26 mod CHAR: A + ] 2map ;
+
+: main ( -- )
+    "Vigenere cipher" dup
+    "Beware the Jabberwock, my son! The jaws that bite, the claws that catch!"
+    2dup "Key: %s\nInput: %s\n" printf
+    vigenere-encrypt dup "Encrypted: %s\n" printf
+    vigenere-decrypt "Decrypted: %s\n" printf ;
+
+MAIN: main