new files

Task/Caesar-cipher/Erlang/caesar-cipher-1.erl

@@ -0,0 +1,33 @@
+%% Ceasar cypher in Erlang for the rosetta code wiki.
+%% Implemented by J.W. Luiten
+
+-module(ceasar).
+-export([main/2]).
+
+%% rot: rotate Char by Key places
+rot(Char,Key) when (Char >= $A) and (Char =< $Z) or
+                   (Char >= $a) and (Char =< $z) ->
+  Offset = $A + Char band 32,
+  N = Char - Offset,
+  Offset + (N + Key) rem 26;
+rot(Char, _Key) ->
+  Char.
+
+%% key: normalize key.
+key(Key) when Key < 0 ->
+  26 + Key rem 26;
+key(Key) when Key > 25 ->
+  Key rem 26;
+key(Key) ->
+  Key.
+
+main(PlainText, Key) ->
+  Encode = key(Key),
+  Decode = key(-Key),
+
+  io:format("Plaintext ----> ~s~n", [PlainText]),
+
+  CypherText = lists:map(fun(Char) -> rot(Char, Encode) end, PlainText),
+  io:format("Cyphertext ---> ~s~n", [CypherText]),
+
+  PlainText = lists:map(fun(Char) -> rot(Char, Decode) end, CypherText).

Task/Caesar-cipher/Erlang/caesar-cipher-2.erl

@@ -0,0 +1 @@
+ceasar:main("The five boxing wizards jump quickly", 3).