Revert demo.odin

code/demo.odin

@@ -1,3 +1,18 @@
+#import "fmt.odin";
+
 main :: proc() {
-	/*
+	immutable program := "+ + * - /";
+	accumulator := 0;
+
+	for token in program {
+		match token {
+		case '+': accumulator += 1;
+		case '-': accumulator -= 1;
+		case '*': accumulator *= 2;
+		case '/': accumulator /= 2;
+		default: // Ignore everything else
+		}
+	}
+
+	fmt.printf("The program \"%s\" calculates the value %d\n", program, accumulator);
 }