explain_entity.h

词法分析器

#include"explain.h"



int explain::FindToken( const char *s)
{
	int first= 0, last = 17,length= strlen(s);
	int m;
	char *cache = new char[length + 1];
	
	for(m = 0; m < length; m++)
		if(s[m] >= 'A' && s[m] <= 'Z')
			cache[m]=tolower(s[m]);       //将大写的字符统一转化为小写
		else
			cache[m] = s[m];
		cache[m] = '\0';
		
		while(first <last+1)
		{
			m = (first + last) / 2;
			if(strcmp(cache, Token_elem[m][1]) == 0)
				return m;
			if(strcmp(cache, Token_elem[m][1]) <0)
				last = m - 1;
			else
				first = m + 1;
		}
		
		return -1;
};


double  explain::calculate( const char *s)
{
	double m=0.0,n=1.0,truevalue=0.0;
	char const *p=s;
	
	while(*p!='\0'&&*p!='.')
	{
		m=*p-'0';
		truevalue=truevalue*10+m;
		p++;
	}
	///////////////////
	if(*p++=='.')
	{
		do
		{
			n/=10.0;
			m=*p-'0';
			truevalue+=m*n;
			p++;
		}while(*p!='\0');
		
		return truevalue;
	}
	
    return truevalue;	
	//
	
};



unsigned explain::letter(char ch)
{
	return ch>='a'&& ch<='z' || ch>='A' && ch<='Z';
};


void  explain::importance(char *ss)
{
	ifstream  s;
	s.open(ss);
	char ch;
	char *cache=new char[100];
	int cnt;
	int  flag;
	
	while(!s.eof())
	{  
		cnt = 0;
		

		do
		{
			ch=s.get();			
		}
		while((ch==' '||ch=='\t'||ch=='\n'));

				
		if(s.eof())
		{
			cout<<"已经到文件结尾了，请重新输入。";
			cout<<'\n';
			return;
		}
		
		cache[cnt++]=ch;

		
		if(letter(ch))
			goto station_1;
		if(isdigit(ch))
			goto station_2;
	
		switch(ch)
		{
		case '*':
			goto station_4;
			break;
		case '/':
			goto station_6;
			break;
		case '-':
			goto station_7;
			break;
		case '+':
		case ',':
		case ';':
		case '(':
		case ')':
			goto station_5;
			break;
		default :break;
		}

		 flag=0;
		 ch=s.get();
		 cnt++;
		goto end;

   station_1:                                 /////标示符
		ch=s.get();
        cache[cnt++]=ch;		
		if (isdigit(ch)||letter(ch))
			goto station_1;
		
			flag=1;
			goto end;
		

		
  station_2:                               ////////数字
		ch=s.get();
		cache[cnt++]=ch;
		if (ch=='.')
			goto station_3;

		if (isdigit(ch))
			goto station_2;

			flag=2;
			goto end;
		


station_3:
		ch=s.get();
		cache[cnt++] = ch;
		if(isdigit(ch))
			goto station_3;

		flag= 3;
		    goto end;



station_4:
		ch=s.get();
		cache[cnt++]=ch;
		if(ch=='-')
			goto station_5;

		flag=3;
		    goto end;

station_5:
		ch=s.get();
	    cnt++;

		flag = 5;
		    goto end;

station_6:
		ch=s.get();
		cache[cnt++] = ch;
		if(ch == '/')
			goto station_5;

	    flag = 6;
		    goto end;
		
station_7:
		ch=s.get();
		cache[cnt++] = ch;
		if(ch == '-')
			goto station_5;

		flag = 7;
		    goto end;
		
end:	
		s.putback(ch);
		cache[cnt - 1] = '\0';
		Token &replace = Token_flow[token_flow_size++];
		
		if(flag == 0)
		{
			replace.type = "error";
			replace.content.caption = new char[100];
			strcpy(replace.content.caption,cache);
			continue;
		}
		
		if(flag == 1)                   //必定为标示符
		{ 
			                               ////比较重要的地方
			replace.content.caption = new char[100];
			strcpy(replace.content.caption,cache);
			
			
			int p = FindToken(cache);	
			if(p == -1)
				replace.type = "error";
			else
			{
				replace.type = Token_elem[p][0];			
				
				if(Token_elem[p][0] == "constant")
				{
					if(Token_elem[p][1] == "pi")
						replace.content.value = 3.1415926;
					if(Token_elem[p][1] == "e")
						replace.content.value = 2.71828;					
					continue;
				}

				
				if(Token_elem[p][0] == "sin")
					replace.content.func = sin;
				if(Token_elem[p][0] == "cos")
					replace.content.func= cos;
				if(Token_elem[p][0] == "tan")
					replace.content.func= tan;
				if(Token_elem[p][0] == "log")
					replace.content.func = log;
				if(Token_elem[p][0] == "exp")
					replace.content.func = exp;
				if(Token_elem[p][0] == "sqrt")
					replace.content.func = sqrt;
					
			
			}
			continue;
		}


		switch(flag)
		{
		case 1:
		    break;
		case 2:
		case 3:
			if(1)
			{
			replace.type = "digit";

		
			replace.content.value = calculate(cache);
			break;
			}
		case 4:
		case 6:
		case 7:
			if(1)
			{
			replace.type = "operator";
			replace.content.caption = new char[100];
			strcpy(replace.content.caption,cache);
			break;
			}
		case 5:
			if(strcmp(cache, "**") == 0)
			{
				replace.type = "power";
				replace.content.caption = new char[100];		
				strcpy(replace.content.caption,cache);
			}
			if(strcmp(cache, "//") == 0 || strcmp(cache, "--") == 0)          //忽略过所有注释
			{
				token_flow_size--;
		    	while(s.get(ch),ch!='\n');		
			}

			if(strcmp(cache, "+") == 0)
			{
				replace.type = "operator";
				replace.content.caption = new char[100];
				strcpy(replace.content.caption,cache);
			}

			if(strcmp(cache, ",") == 0 || strcmp(cache, ";") == 0 || strcmp(cache, "(") == 0 || strcmp(cache, ")") == 0)
			{
				replace.content.caption = new char[100];
				strcpy(replace.content.caption,cache);
				replace.type =new char[100];
				strcpy(replace.type,cache);			
			}
			break;

		default:
			break;
			}		
	}


	
}




void explain::RestoreResult(char *file)
{
	ofstream fout(file);
	for(int i = 0; i < token_flow_size; i++)
	{
		fout << setw(15) << i << setw(20) << Token_flow[i].type;
		if(Token_flow[i].type == "const" || Token_flow[i].type == "digit")
		{
			fout << setw(20) << Token_flow[i].content.value << endl;
			continue;
		}
		
		if(Token_flow[i].type == "function")
		{
			fout << setw(20) << Token_flow[i].content.func << endl;
			continue;
		}
		
		fout << setw(20) << Token_flow[i].content.caption << endl;					
	}
}