modified:   tree/Constant.java
	modified:   tree/Ex1.java
	modified:   tree/Ex2.java
	new file:   tree/Ex3.java
	new file:   tree/Ex4.java
	modified:   tree/Expression.java
	modified:   tree/Operation.java
	modified:   tree/Operator.java
	modified:   tree/Variable.java
	new file:   tree/antlr-runtime-4.2.jar
	new file:   tree/expr.jar