#include<string.h>


	char* reserve[21]={"and","begin","const","div","do","else","end","function","if","integer",		
		"not","or","procedure","program","read","real","then","type","var","while","write"};	//保留字表
	
	int num[30];			//常量表
	int const_tab=0;		//常量表當前大小
	char line[100];			//放入文件的一行
	static int ii=0,jj=0;	//當前文件讀頭位置，行未標志
	int lineno=1;			//行號
	extern char token[11];			//標識符的緩沖區(qū)

int scanner(ifstream&);
void getnbc(ifstream&, char&);
void getchar(ifstream&, char&);
int search_reserve(char*);
int search_symbol(char*);
int search_num(char*);
void retract(char&);
int getconst();	//當剛掃描到一個數(shù)時，此函數(shù)用來反回其編號，若常量數(shù)組中已經(jīng)有該數(shù)，則已有地址

	


int scanner(ifstream& sf)
{
	int token_num=0;	//緩沖區(qū)當前大小
	int temp=0;
	char current;
	getnbc(sf,current);

	switch(current)
	{
	case'a':
	case'b':
	case'c':
	case'd':
	case'e':
	case'f':
	case'g':
	case'h':
	case'i':
	case'j':
	case'k':
	case'l':
	case'm':
	case'n':
	case'o':
	case'p':
	case'q':
	case'r':
	case's':
	case't':
	case'u':
	case'v':
	case'w':
	case'x':
	case'y':
	case'z':	token[token_num]=current;	
				token_num++;
				getchar(sf,current);
				while((current<='z'&&current>='a')||(current<='9'&&current>='0'))
				{
					if(token_num<10)
					{
						token[token_num]=current;
						token_num++;
					}
					getchar(sf,current);
				}
				token[token_num]='\0';
				retract(current);
				temp=search_reserve(token);
				if(temp==-1)
				{
					return 21;
				}
				else
				{
					return temp;
				}
				break;

	case'0':
	case'1':
	case'2':
	case'3':
	case'4':
	case'5':
	case'6':
	case'7':
	case'8':
	case'9':
				temp=current-30;		//char到int的轉(zhuǎn)變
				getchar(sf,current);
				while(current<='9'&&current>='0')
				{
					if(temp<65535)
					{
						temp=temp*10+(current-30);	//char到int的轉(zhuǎn)變
					}
					getchar(sf,current);
				}
				num[const_tab++]=temp;
				retract(current);
				return 22;
				break;
	case',':	
				return 23;
	case';':
				return 24;
	case':':	getchar(sf,current);
				if(current=='=')
				{
					
					return 44;
				}else
				{
					retract(current);
					
					return 25;
				}
	case'.':	getchar(sf,current);
				if(current=='.')
				{
					return 31;
				}else
				{
					retract(current);
					return 26;
				}
	case'(':
				return 27;
	case')':
				return 28;
	case'[':
				return 29;
	case']':
				return 30;
	//缺單目加
	//缺單目減
	case'+':	
				return 34;
	case'-':
				return 35;	
	case'*':
				return 36;
	case'/':
				return 37;	
	case'=':	
				return 38;
	case'<':	getchar(sf,current);
				if(current=='>')
				{
					return 41;
				}
				if(current=='=')
				{
					return 42;
				}
				else
				{
					retract(current);
					return 39;
				}
	case'>':	getchar(sf,current);
				if(current=='=')
				{
					return 43;
				}else
				{
					retract(current);
					return 40;
				}
	case'{':
				return 45;
	case'}':	
				return 46;
	case'#':
				return 47;
	default:
				return -1;
	}
}

void getnbc(ifstream& sf, char& current)
{
GET:	getchar(sf,current);
	
	if(current==' '||current=='\0'||current=='\t')
	{
		do{
			getchar(sf,current);
		}while(current==' '||current=='\0'||current=='\t');
	}
	
	if(current=='{')
	{
		do{
			getchar(sf,current);
		}while(current!='}');
		goto GET;
	}

	
}

void getchar(ifstream& sf, char& current)
{
	if(ii==jj)
	{
		ii=jj=0;
		sf.getline(line,100);
		
		for( ;line[jj]!='\0';jj++);

		lineno=lineno+1;
		current=line[ii];
		return;
	}
	
	current=line[++ii];
	if(current>='A'&&current<='Z')
		current+=32;
}

int search_reserve(char* token)
{
	for(int i=0;i<=20;i++)
	{
		if(strcmp(token,reserve[i])==0)
			return i;
	}
	
	return -1;
}


void retract(char& current)
{
	ii--;
	current=line[ii];
}

int getconst()
{
	for(int i=0;i<const_tab-1;i++)
	{
		if(num[i]==num[const_tab-1])
		{
			const_tab-=1;
			return 1000+i;
		}
	}
	return 999+const_tab;
}