ifstatementnode.java

是有关解释器的.用JAVA编写.可以解释一般的JAVA程序.

class IfStatementNode extends ExecutableNode
{
	OrClauseNode vOrClauseNode;
	StatementNode vFirstStatementNode;
	StatementNode vSecondStatementNode;
	Value vOrClauseValue;
	
	static IfStatementNode parserIfStatement(Environment env, Scanner s) throws ParserException, ScannerException
	{
		OrClauseNode tmpOrClauseNode;
		StatementNode tmpFirstStatementNode;
		StatementNode tmpSecondStatementNode= null;
		
		matchKeyword(s,"if");
		matchBracket(s,'(');
		tmpOrClauseNode= OrClauseNode.parserOrClause(env,s);
		matchBracket(s,')');
		tmpFirstStatementNode= StatementNode.parserStatement(env,s);
		if(isKeywordToken(s,"else"))
		{
			matchKeyword(s,"else");
			tmpSecondStatementNode= StatementNode.parserStatement(env,s);
		}
		
		return new IfStatementNode(tmpOrClauseNode, tmpFirstStatementNode, tmpSecondStatementNode);		
	}
	static boolean mIsIfStatement(Scanner s) throws ScannerException
	{
		return isKeywordToken(s,"if");
	}
	IfStatementNode()
	{
		vOrClauseNode= null;
		vFirstStatementNode= null;
		vSecondStatementNode= null;
	}
	IfStatementNode(OrClauseNode aOrClauseNode, StatementNode aFirstStatementNode, StatementNode aSecondStatementNode)
	{
		vOrClauseNode= aOrClauseNode;
		vFirstStatementNode= aFirstStatementNode;
		vSecondStatementNode= aSecondStatementNode;
	}
	String format(int indent)
	{
		String str=space(indent)+"if(" + vOrClauseNode.format(indent)+")\n" +
					space(indent) + vFirstStatementNode.format(indent);
		if(vSecondStatementNode!=null)
			str+= space(indent)+"else\n"+space(indent)+vSecondStatementNode.format(indent);
		return str;
	}
	Environment run(Environment env) throws InterpreterException
	{			
		BooleanValue tmpValue= (BooleanValue)vOrClauseValue;
		if(tmpValue.booleanValue())vFirstStatementNode.run(env);
				else if(vSecondStatementNode!=null)
						env= vSecondStatementNode.run(env);
		
		return env;
	}
	boolean typeCheck(Environment env) throws InterpreterException
	{
		if(vOrClauseNode.typeCheck(env))
		{
			vOrClauseValue= vOrClauseNode.evaluate(env);		
			if(vOrClauseValue.isBoolean())				
				if(vFirstStatementNode.typeCheck(env))				
					if(vSecondStatementNode!=null)return vSecondStatementNode.typeCheck(env);
					else return true;
				else ProgramNode.mTypeCheckError(this.format(4));
			else ProgramNode.mTypeCheckError(this.format(4));		
		}else ProgramNode.mTypeCheckError(this.format(4));		
		
		return true;
	}
}