Data commit

Task/Caesar-cipher/R/caesar-cipher.r

@@ -0,0 +1,26 @@
+# based on Rot-13 solution: http://rosettacode.org/wiki/Rot-13#R
+ceasar <- function(x, key)
+{
+  # if key is negative, wrap to be positive
+  if (key < 0) {
+    key <- 26 + key
+  }
+
+  old <- paste(letters, LETTERS, collapse="", sep="")
+  new <- paste(substr(old, key * 2 + 1, 52), substr(old, 1, key * 2), sep="")
+  chartr(old, new, x)
+}
+
+# simple examples from description
+print(ceasar("hi",2))
+print(ceasar("hi",20))
+
+# more advanced example
+key <- 3
+plaintext <- "The five boxing wizards jump quickly."
+cyphertext <- ceasar(plaintext, key)
+decrypted <- ceasar(cyphertext, -key)
+
+print(paste("    Plain Text: ", plaintext, sep=""))
+print(paste("   Cypher Text: ", cyphertext, sep=""))
+print(paste("Decrypted Text: ", decrypted, sep=""))