@@ -0,0 +1,237 @@
+%0Apublic class Zero extends Node %7B%0A%0A%09@Override%0A%09public Value interp(Scope s) %7B%0A%09%09return new IntValue(0);%0A%09%7D%0A%0A%09@Override%0A%09public Value typecheck(Scope s) %7B%0A%09%09return Type.INT;%0A%09%7D%0A%09%0A%09@Override%0A%09public String toString() %7B%0A%09%09return %220%22;%0A%09%7D%0A%0A%7D%0A

support +a, +3, -2, -a eg: -3 to 0 - 3 ...