Data commit

Task/Caesar-cipher/Ada/caesar-cipher.ada

@@ -0,0 +1,45 @@
+with Ada.Text_IO;
+
+procedure Caesar is
+
+   type modulo26 is modulo 26;
+
+   function modulo26 (Character: Character; Output: Character) return modulo26 is
+   begin
+      return modulo26 (Character'Pos(Character)+Character'Pos(Output));
+   end modulo26;
+
+   function Character(Val: in  modulo26; Output: Character)
+                        return Character is
+   begin
+      return Character'Val(Integer(Val)+Character'Pos(Output));
+   end Character;
+
+   function crypt (Playn: String; Key: modulo26) return String is
+      Ciph: String(Playn'Range);
+
+   begin
+      for I in Playn'Range loop
+         case Playn(I) is
+            when 'A' .. 'Z' =>
+               Ciph(I) := Character(modulo26(Playn(I)+Key), 'A');
+            when 'a' .. 'z' =>
+               Ciph(I) := Character(modulo26(Playn(I)+Key), 'a');
+            when others =>
+               Ciph(I) := Playn(I);
+         end case;
+      end loop;
+      return Ciph;
+   end crypt;
+
+   Text:  String := Ada.Text_IO.Get_Line;
+   Key: modulo26 := 3; -- Default key from "Commentarii de Bello Gallico" shift cipher
+
+begin -- encryption main program
+
+   Ada.Text_IO.Put_Line("Playn ------------>" & Text);
+   Text := crypt(Text, Key);
+   Ada.Text_IO.Put_Line("Ciphertext ----------->" & Text);
+   Ada.Text_IO.Put_Line("Decrypted Ciphertext ->" & crypt(Text, -Key));
+
+end Caesar;