parsertable.java

实验软装置（基于表达式的计算器ExprEval） 很不错的 有帮助于学习提高

package parser;
import exceptions.*;
import java.io.BufferedReader;
import java.io.FileInputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.util.ArrayList;
import scanner.*;
public class ParserTable {



	/**
	 * get the type of error when one type meets another
	 * @param stack token type in thestack
	 * @param input lookahead token type
	 * @return
	 */
	public ExpressionException getError(int stack,int input)
	{
		switch(stack)
		{ 
		case TokenType.NUMBER:
			if(input==TokenType.NUMBER||input==TokenType.LBRACKET||input==TokenType.SIN||input==TokenType.COS
					||input==TokenType.MAX||input==TokenType.MIN||input==TokenType.NOT||input==TokenType.BOOL){
				return new exceptions.MissingOperatorException();
			}
			break;
		case TokenType.COLON:
			if(input==TokenType.COLON){
				return new exceptions.TrinaryOperationException();
			}
		case TokenType.LBRACKET:
		    if(input==TokenType.END)
		    {
		    	return new exceptions.MissingRightParenthesisException();
		    }
		    break;
		case TokenType.RBRACKET:
			if(input==TokenType.NUMBER||input==TokenType.SIN||input==TokenType.COS||input==TokenType.LBRACKET
					||input==TokenType.MAX||input==TokenType.MIN||input==TokenType.NOT||input==TokenType.BOOL)
			{
				return new exceptions.MissingOperatorException();
			}
			break;
		case TokenType.QMARK:
			if(input==TokenType.END)
				return new exceptions.TrinaryOperationException();
			break;
		case TokenType.BOOL:
			if(input==TokenType.NUMBER||input==TokenType.SIN||input==TokenType.COS||input==TokenType.LBRACKET
					||input==TokenType.MAX||input==TokenType.MIN||input==TokenType.NOT||input==TokenType.BOOL)
			{
				return new exceptions.MissingOperatorException();
			}
			break;		
		case TokenType.END:
			if(input==TokenType.RBRACKET){
				return new exceptions.MissingLeftParenthesisException();
				
			}
			else if(input==TokenType.COLON){
				return new exceptions.TrinaryOperationException();
			}
			break;
		}
		return new exceptions.MissingOperandException();
		
	}
	/**
	 * judge whether one type meet another causes an error
	 * @param stack the token type in the stack
	 * @param input the lookahead type
	 * @return true if error
	 */
	public boolean isError(int stack,int input)
	{
		switch(stack)
		{ 
		case TokenType.NUMBER:
			if(input==TokenType.NUMBER||input==TokenType.LBRACKET||input==TokenType.SIN||input==TokenType.COS
					||input==TokenType.MAX||input==TokenType.MIN||input==TokenType.NOT||input==TokenType.BOOL){
				return true;
			}
			break;
		case TokenType.LBRACKET:
		    if(input==TokenType.END)
		    {
		    	return true;
		    }
		    break;
		case TokenType.COLON:
			if(input==TokenType.COLON){
				return true;
			}
			break;
		case TokenType.RBRACKET:
			if(input==TokenType.NUMBER||input==TokenType.SIN||input==TokenType.COS||input==TokenType.LBRACKET
					||input==TokenType.MAX||input==TokenType.MIN||input==TokenType.NOT||input==TokenType.BOOL)
			{
				return true;
			}
			break;
		case TokenType.QMARK:
			if(input==TokenType.END)
				return true;
			break;
		case TokenType.BOOL:
			if(input==TokenType.NUMBER||input==TokenType.SIN||input==TokenType.COS||input==TokenType.LBRACKET
					||input==TokenType.MAX||input==TokenType.MIN||input==TokenType.NOT||input==TokenType.BOOL)
			{
				return true;
			}
			break;
		case TokenType.END:
			if(input==TokenType.RBRACKET||input==TokenType.COLON){
				return true;
				
			}
			break;
		}
		return false;
	}
    /**
     * judge whether to shift or reduce
     * @param input token type in the stack
     * @param lookahead lookahead token type
     * @return true if shift
     */
    public static boolean isShift(int input,int lookahead)
    {
    	if(lookahead==TokenType.LBRACKET||input==TokenType.LBRACKET)
    		return true;
    	if(input==TokenType.RBRACKET||lookahead==TokenType.RBRACKET)
    		return false;
    	
        if(input==TokenType.COLON&&lookahead==TokenType.QMARK){
        	return true;
        }
        if(input==TokenType.QMARK&&lookahead==TokenType.COLON){
        	return true;
        }
        if(input==TokenType.QMARK&&lookahead==TokenType.QMARK){
        	return true;
        }
      
    	if(TokenType.getPriority(input)==TokenType.getPriority(lookahead)){
    		if(TokenType.isLeft(input))
    			return true;
    		else
    			return false;
    	}
    	
    	if(TokenType.getPriority(input)<TokenType.getPriority(lookahead)){
    		return false;
    	}
    	else return true;
    	
    }
}