//Parser2- Example of Recursive Descent Parser
//Program Limitation: Tokens must be separated with space(s) 
//Program by Barimani--Date 9/22/2009

#include <iostream>
#include <fstream>
#include<cctype>
using namespace std;
#define B_ERR "..Initial BEGIN is missing\n****Rejected****\n";
#define E_ERR "..Expected to see END\n****Rejected****\n";
#define EC_ERR "..Characters after END\n****Rejected****\n";
#define EQ_ERR "..Expect to see an Equal\n****Rejected****\n";
#define EXP_ERR "..Expect to see an Expression\n****Rejected****\n";

#define root "<Block> -> Begin <Sts> End\n";
#define stree1 "<Sts> -> Id = <E> <Sts>\n";
#define stree2 "<Sts> -> empty\n";
//#define etree "<E> -> Id <E'>\n";
//#define exptree1 "<E'> -> + Id <E'>\n";
//#define exptree2 "<E'> -> - Id <E'>\n";
//#define exptree3 "<E'> -> empty\n";


ifstream f1;

void gettoken(char* token)
{
   if (!f1.eof()) f1>>token;
   int l= strlen(token);
   for (int i=0; i< l; i++)
	   token[i]= toupper(token[i]);
   
}

void E(char* token)
{
  if(strcmp(token,"E") != 0)
  {
		cout<<EXP_ERR;
		system("PAUSE");
		exit(1);
  }
  
}

void Sts(char* token)
{
  gettoken(token);
  if(strcmp(token,"ID") != 0)
  {
		cout<<stree2;
  }
  else
  {
	cout<<stree1;
	gettoken(token);
	if(strcmp(token,"=") != 0)
	{
		cout<<EQ_ERR;
		system("PAUSE");
		exit(0);
	}
	gettoken(token);
	E(token);
	Sts(token);
  }	
}

int main()
{
	char token[10];
	f1.open("test1.txt", ios::in);
	if (f1.fail())
	{
		cout<<"cannot open file!!\n";
		system("PAUSE");
		exit(1);
	}	
	gettoken(token);
	cout<<root;
	if(strcmp(token,"BEGIN") != 0)
	{
		cout<<B_ERR;
		system("PAUSE");
		exit(0);
	}
	
	Sts(token);
   
	if (strcmp(token,"END") != 0)
	{
		cout<<E_ERR;
		system("PAUSE");
		exit(0);
	}
	if (f1.eof())
		cout<<"***Accepted***\n";
	else
		cout<<EC_ERR;
	f1.close();
	system("PAUSE");
	return 0;
}