assignmentstatementnode.java

是有关解释器的.用JAVA编写.可以解释一般的JAVA程序.

class AssignmentStatementNode extends ExecutableNode
{
	IdentifierNode vIdentifierNode;
	ExpressionNode vExpressionNode;
	Value vExpressionValue;
	
	static AssignmentStatementNode parserAssignmentStatement(Environment env, Scanner s) throws ParserException, ScannerException
	{
		IdentifierNode tmpIdentifierNode;
		ExpressionNode tmpExpressionNode;
		
		tmpIdentifierNode= IdentifierNode.parserIndentifier(env,s);
		matchSimple(s,'=');
		tmpExpressionNode= ExpressionNode.parserExpression(env,s);
		matchSimple(s,';');
		
		return new AssignmentStatementNode(tmpIdentifierNode, tmpExpressionNode);
	}
	static boolean mIsAssignmentStatement(Scanner s) throws ScannerException
	{
		Token t= s.followingToken();
		if(t.isSimple())return ((SimpleToken)t).isAssign();
			else return false;		
	}
	AssignmentStatementNode()
	{
		vIdentifierNode= null;
		vExpressionNode= null;
	}
	AssignmentStatementNode(IdentifierNode aIdentifierNode, ExpressionNode aExpressionNode)
	{
		vIdentifierNode= aIdentifierNode;
		vExpressionNode= aExpressionNode;
	}
	Environment run(Environment env) throws InterpreterException
    {	
		if(env.exists(vIdentifierNode.vName))
			env.updateValue(vIdentifierNode.vName,vExpressionNode.evaluate(env));
		else ProgramNode.mTypeCheckError(this.format(4) + "\nUndefine variable" + vIdentifierNode.vName);
		
		return env;
    }
    String format(int indent)
    {
    	String str= vIdentifierNode.format(indent);
    	if(vExpressionNode!=null)
    		str+= "="+vExpressionNode.format(indent);
        return space(indent) + str + ";\n";
    }
    boolean typeCheck(Environment env) throws InterpreterException
	{    	    	
    	if(vExpressionNode.typeCheck(env))
    	{
    		vExpressionValue= vExpressionNode.evaluate(env);    		    		
    		if(!vExpressionValue.getClass().getName().equals(env.at(vIdentifierNode.vName).getClass().getName()))
    				ProgramNode.mTypeCheckError(this.format(4));
    	}else ProgramNode.mTypeCheckError(this.format(4));    	
		
		return true;
	}
}