for.cpp

一个简单的语法分析器,实现对布尔表达式,算术表达式的分析,以及if语句,FOR语句,WHILE语句,DO_WHILE语句的分析

//分析for循环语句
#include "Parser.h"
int Sen_For()
{
	int RTN_ADDR = lineOfEqu + 1;
	GetNextSymble();
	int initValue = Sen_Assign();
	int targetValue = 0;
	int rtn1 = 0;
	if(curr_code == 22)          //是否为to
	{
		GetNextSymble();
		if(curr_code == 27 || curr_code == 28)         //为整数或标志符
		{
			targetValue = curr_addr;
			GetNextSymble();
			if(curr_code == 8)                        //是否为do
			{
				GetNextSymble();
				int TRUE_ADDR = EquPush(10, initValue, targetValue, 0);
				int FALSE_ADDR = EquPush(6, 0, 0, 0);
				switch(curr_code)
				{
				case 27:                      //标志符,说明是赋值语句
					Sen_Assign();
					rtn1 = expr_rtn_addr;
					break;
				case 12:
					rtn1 = Sen_For();             //for语句
					break;
				case 13:                       //if语句
					rtn1 = Sen_If();
					break;
				case 20:                       //repeat循环语句
					rtn1 = Sen_Repeat();
					break;
				case 26:                        //while循环语句
					rtn1 = Sen_While();
					break;
				case 2:                         //begin
					rtn1 = Begin();
					break;
				default:                        //其他语句为错误
					Error(COMMON_ERROR);
					break;
				}
				BackPatch(TRUE_ADDR, rtn1);
				int tt = New_Temp();
				EquPush(2, initValue, ONE, tt);
				EquPush(1, tt, 0, initValue);
				EquPush(6, 0, 0, RTN_ADDR);
				BackPatch(FALSE_ADDR, lineOfEqu + 1);
			}
			else
			{
				Error(FOR_ERROR);
			}
		}
		else
		{
			Error(FOR_ERROR);
		}
	}
	else
	{
		Error(FOR_ERROR);
	}
	return RTN_ADDR;
}