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Task/Caesar-cipher/Ursa/caesar-cipher.ursa

@@ -0,0 +1,28 @@
+decl string mode
+while (not (or (= mode "encode") (= mode "decode")))
+	out "encode/decode: " console
+	set mode (lower (in string console))
+end while
+
+decl string message
+out "message:       " console
+set message (upper (in string console))
+
+decl int key
+out "key:           " console
+set key (in int console)
+if (or (> key 26) (< key 0))
+	out endl "invalid key" endl console
+	stop
+end if
+
+if (= mode "decode")
+	set key (int (- 26 key))
+end if
+
+for (decl int i) (< i (size message)) (inc i)
+	if (and (> (ord message<i>) 64) (< (ord message<i>) 91))
+		out (chr (int (+ (mod (int (+ (- (ord message<i>) 65) key)) 26) 65))) console
+	end if
+end for
+out endl console