songwei.cpp

1. 系统功能：能读取词法分析结果进行语法分析

#include<iostream.h>
#include<fstream.h>
#include<string.h>
#define $XIAOYU		0		//<
#define $DAYU		1		//>
#define $DENG		4		//=
#define $IF			6		//IF
#define $if			7		//if
#define $THEN		8		//THEN
#define $then		9		//then
#define $ID			10		//标志符
#define $NUM		11		//数字

typedef struct Token
{
	int type;			//类型
	char ch;			//值
}Token;
Token cur;
#define MAX_TOKEN 256 //Token表大小

Token tokentable[MAX_TOKEN];
int token_index;	//token表索引
int total_len;		//token表有效长度
struct
{
	char str[10];
}stack[80],buffer[80];
int pom=0;			//栈指针
int inc=0; 
ifstream shuru;
bool init(char filename[255]);
bool cifa();
void S();
void E();
bool nexttoken();
void print();
void push(char arg[8]);
void pop();
int main()
{
	cout<<"Please input the file which wants to be compiled: ";		
	char fname[200];
	cin>>fname;
	if(!init(fname))
		return 1;
	if(!cifa())
		return 1;
	char ch;
	while(1)
	{
		if(shuru.eof()) //如果文件结束
			break;
		shuru>>ch;
	}
	cout<<"使用的文法为:"<<endl;
	cout<<"S->E|if E then S"<<endl;
	cout<<"E->T<T|T>T|T=T"<<endl;
	cout<<"T->id|num"<<endl;
	nexttoken();
	cout<<"所使用的产生式:"<<endl;
	S();
	cout<<"逆波兰式:"<<endl;
	print();
	return 0;
}

bool init(char filename[200])			//打开文件
{
	token_index=0;
	total_len=0;
	shuru.open(filename,ios::nocreate|ios::in);
	if(!shuru)
	{
		cout<<"文件打开出错!"<<endl;
		return false;
	}
	else
		return true;
}

bool cifa()
{
	char buf[16];
	char ch;
	while(1)
	{
		shuru>>ch;
		if(!shuru)
			break;
		else if(ch=='<')
		{	
			tokentable[total_len].type=$XIAOYU;
			tokentable[total_len++].ch=ch;
		}
		else if(ch=='>')
		{
			tokentable[total_len].type=$DAYU;
			tokentable[total_len++].ch=ch;
		}
		else if(ch=='=')
		{
			tokentable[total_len].type=$DENG;
			tokentable[total_len++].ch=ch;
		}
		else if(ch=='I')
		{
			shuru>>buf;
			if(strcmp(buf,"F")==0)
				tokentable[total_len].type=$IF;
				tokentable[total_len++].ch=0;
		}
		else if(ch=='i')
		{
			shuru>>buf;
			if(strcmp(buf,"f")==0)
				tokentable[total_len].type=$if;
				tokentable[total_len++].ch=0;
		}
		else if(ch=='T')
		{
			shuru>>buf;
			if(strcmp(buf,"HEN")==0)
				tokentable[total_len].type=$THEN;
				tokentable[total_len++].ch='$';
		}
		else if(ch=='t')
		{
			shuru>>buf;
			if(strcmp(buf,"hen")==0)
				tokentable[total_len].type=$then;
				tokentable[total_len++].ch='$';
		}
		else if(ch>='a' && ch<='z')
		{
			tokentable[total_len].type=$ID;
			tokentable[total_len++].ch=ch;
		}
			else if(ch>='0' && ch<='9')
		{
			tokentable[total_len].type=$NUM;
			tokentable[total_len++].ch=ch;
		}
	}
	token_index=0;
	return true;
}

void S()
{

	if((cur.type==$ID)||(cur.type==$NUM))
	{
		char a[8],b[8],c[8];
		cout<<"S->"<<cur.ch;
		*a=cur.ch;
		*(a+1)='\0';
		if(!nexttoken())
			cout<<"There is only one operand"<<endl;
		if((cur.type!=$DENG)&&(cur.type!=$DAYU)&&(cur.type!=$XIAOYU))
			cout<<"Lack of operator"<<endl;
		cout<<cur.ch;
		*c=cur.ch;
		*(c+1)='\0';
		if(!nexttoken())
			cout<<"Lack of operand"<<endl;
		if((cur.type!=$ID)&&(cur.type!=$NUM))
			cout<<"Lack of operand"<<endl;
		cout<<cur.ch<<endl;
		*b=cur.ch;
		*(b+1)='\0';
		push(c);
		push(b);
		push(a);
		pop();
		pop();
		pop();
		nexttoken();
	}

	else if((cur.type==$IF)||(cur.type==$if))
	{
		if(!nexttoken())
			cout<<"There is nothing behind the keyword if"<<endl;
		{
			cout<<"S->if E then S "<<endl;
			E();
			if((cur.type==$then)||(cur.type==$THEN))
			{	char d[8];
				*d=cur.ch;
				*(d+1)='\0';
				push(d);
				pop();
				if(!nexttoken())
				cout<<"There is nothing behind the keyword then"<<endl;
				S();
			}
			else
				cout<<"Lack of then"<<endl;
		}
	}
}

void E()
{
	if((cur.type==$ID)||(cur.type==$NUM))
	{
		char a[8],b[8],c[8];
		*a=cur.ch;
		*(a+1)='\0';
		cout<<"E->"<<cur.ch;
		if(!nexttoken())
			cout<<"There is nothing before E"<<endl;
		if((cur.type!=$DENG)&&(cur.type!=$DAYU)&&(cur.type!=$XIAOYU))
			cout<<"Lack of operator"<<endl;
		cout<<cur.ch;
		*c=cur.ch;
		*(c+1)='\0';
		if(!nexttoken())
			cout<<"Lack of operand"<<endl;
		if((cur.type!=$ID)&&(cur.type!=$NUM))
			cout<<"Lack of operand"<<endl;
		cout<<cur.ch<<endl;
		*b=cur.ch;
		*(b+1)='\0';	
		push(c);				//让操作符进栈
		push(b);				//让第二个操作数进栈
		push(a);				//让第一个操作数进栈
		pop();
		pop();
		pop();
		if(!nexttoken())
			cout<<"Lack of then!"<<endl;
	}
	else
		cout<<"E(),error!"<<endl;
}

void push(char arg[8])
{	
strcpy(stack[pom].str,arg);
pom++;
}

void pop()
{
strcpy(buffer[inc].str,stack[pom-1].str);
inc++;
pom--;
}

bool nexttoken()
{
	if(token_index>=total_len)
		return false;
	else
	{
		cur.type=tokentable[token_index].type;
		cur.ch=tokentable[token_index].ch;
		token_index++;
		return true;
	}
}

void print()
{
	for(inc=0;inc<80;inc++)
	cout<<buffer[inc].str;

}