#include <stdio.h>
#include <ctype.h>
//#include<iostream>
#include<math.h>
//using namespace std;



//E -> TE' 
//E' -> +TE' | e
//T -> FT'
//T' -> *FT' | e
//F -> NUM | (E)
//FIRST(E) = {NUM, LEFTB}
//FIRST(E') = {PLUS, e}
//FIRST(T) = {NUM, LEFTB}
//FIRST(T') = {MULT, e}
//FIRST(F) = {NUM, LEFTB}
//FOLLOW(E) = {$, RIGHTB}
//FOLLOW(E') = {$, RIGHTB}
//FOLLOW(T) = {PLUS, RIGHTB, $}
//FOLLOW(T') = {PLUS, RIGHTB, $}
//FOLLOW(F) = {MULT, PLUS, RIGHTB, $}

enum TOKEN {PLUS, MULT, NUM, END, ERR, LEFTB, RIGHTB};
char lookahead;
enum TOKEN token;
int num;
int error = 0;
FILE *fp;

void lexical(FILE *fp);
int match(enum TOKEN x);
int E();
int E_();
int T();
int T_();
int F();


//return 0 if success, return 1 otherwise
int match(enum TOKEN x) {
	if(token == x) {
		lexical(fp);
		return 0;
	} else {
		error = 1;
		return 1;
	}
}

//E -> TE' 
int E() {
	switch (token)
	{
	case LEFTB: case NUM:
		return T() + E_();//一旦匹配到E_()就得 加上所匹配的东西
	default:
		error = 1;//报错
		printf("error E()");
		break;
	}
	return 0;
}

//E_ -> +TE'|e 
int E_() {
	switch (token)
	{
	case PLUS:
		match(PLUS); return T() + E_();//由于T()后面是E_()所以加上自身
	case RIGHTB: case END:
		return 0;//加上0 和不变
	default:
		error = 1;//报错
		printf("error E_()");
		break;
	}
	return 0;
}

//T -> FT'
int T() {
	switch (token)
	{
	case LEFTB: case NUM:
		return F()*T_();
	default:
		error = 1;//报错
		printf ("error T()");
		break;
	}
	return 0;
}


//T' -> *FT' | e
int T_() {
	switch (token)
	{
	case MULT:
		match(MULT); return F()*T_();
	case PLUS: case RIGHTB: case END:
		return 1;
	default:
		error = 1;//报错
		printf( "error T_()") ;
		break;
	}
	return 0;
}

//F -> NUM | (E)
int F() {
	double temp;//用于保存E()的值
	switch (token)
	{
	case LEFTB: 
		match(LEFTB);
		temp = E();
		match(RIGHTB);
		return temp;
	case NUM:
		temp = num;
		match(NUM);
		return temp;
	default:
		error = 1;//报错
		printf("error F()");
		break;
	}
	return 0;
}

//读入文本，保存记号流，将记号保存在 token 中，数字 保存在NUM 中
void lexical(FILE *fp) {

	lookahead = getc(fp);
	num = 0;

	while (lookahead == ' ' || lookahead == '\t' || lookahead == '\n') {
		lookahead = getc(fp);
	}

	if (isdigit(lookahead)) {
		int count = 0;
		if (isdigit(lookahead) || lookahead == '.'){
			num = 0;
			while (isdigit(lookahead)) {
				token = NUM;
				num = num * 10 + lookahead - '0';//相当于左移一位
				lookahead = getc(fp);
			}
			if (lookahead == '.'){
				lookahead = getc(fp);
				while (isdigit(lookahead)){
					num = num * 10 + lookahead - '0';//相当于左移一位
					lookahead = getc(fp);
					count++;
				}
				num = (num * (pow(0.1,count)));//移动小数点
			}
			ungetc(lookahead, fp);//回退一步
			return;
		}
	}
	else if (lookahead == '+') {
		token = PLUS;
		return;
	}
	else if (lookahead == '*') {
		token = MULT;
		return;
	}
	else if (lookahead == EOF) {
		token = END;
		return;
	}
	else if (lookahead == '(') {
		token = LEFTB;//左括号
		return;
	}
	else if (lookahead == ')') {
		token = RIGHTB;//右括号
		return;
	}
	else {
		error = 1;//有错误
		token = ERR;
		return;
	}
}

//F -> NUM | (E)






int main(int argc, char **argv) {
	int  res = 0;
	if(argc < 2) {
		printf("insufficient arguments");
		return 1;
	}
	fp = fopen(argv[1], "r");

	lexical(fp);
	res = E();
	if(!error) {
		printf("%d\n", res);
	} else {
		printf("There are errors\n");
	}

	fclose(fp);
	return 0;

}