Data commit

Task/Vigen-re-cipher/R/vigen-re-cipher.r

@@ -0,0 +1,18 @@
+mod1 = function(v, n)
+# mod1(1:20, 6)   =>   1 2 3 4 5 6 1 2 3 4 5 6 1 2 3 4 5 6 1 2
+    ((v - 1) %% n) + 1
+
+str2ints = function(s)
+    as.integer(Filter(Negate(is.na),
+        factor(levels = LETTERS, strsplit(toupper(s), "")[[1]])))
+
+vigen = function(input, key, decrypt = F)
+   {input = str2ints(input)
+    key = rep(str2ints(key), len = length(input)) - 1
+    paste(collapse = "", LETTERS[
+        mod1(input + (if (decrypt) -1 else 1)*key, length(LETTERS))])}
+
+message(vigen("Beware the Jabberwock, my son! The jaws that bite, the claws that catch!", "vigenerecipher"))
+  # WMCEEIKLGRPIFVMEUGXQPWQVIOIAVEYXUEKFKBTALVXTGAFXYEVKPAGY
+message(vigen("WMCEEIKLGRPIFVMEUGXQPWQVIOIAVEYXUEKFKBTALVXTGAFXYEVKPAGY", "vigenerecipher", decrypt = T))
+  # BEWARETHEJABBERWOCKMYSONTHEJAWSTHATBITETHECLAWSTHATCATCH