a.cpp

利用vc制作的模拟编译器的扫描程序

#include<ctype.h>
#include<string.h>
#include<stdio.h>
struct node
{ int code;char value[32];};
char buffer[100];
char * respoint=buffer;
char keepword[5][20]={"BEGIN","IF","THEN","ELSE","END"};
char nametable[100][32];
char consttable[100][32];
int temp1=0,temp2=0;
char ch;
char strstoken[32];
void GetChar()
{
	ch=*respoint;
	respoint++;
	return;
}
void GetBC()
{
	while(ch==' '){
		ch=*respoint;
		respoint++;
	}
}
void Concat()
{
	strncat(strstoken,&ch,1);
}
int Reserve()
{
	for(int i=0;i<5;i++)
		if(!strcmp(strstoken,keepword[i]))
			return i+1;
		return 0;
}
void Retract()
{
	respoint--;
	ch=' ';
}
char * Insertid()
{
	temp1++;
	strcpy(nametable[temp1],strstoken);
	return nametable[temp1];
}
char * Insertconst()
{
	temp2++;
	strcpy(consttable[temp2],strstoken);
	return consttable[temp2];
} 
struct node scan()
{
	int code1;
	struct node tem;
	strcpy(strstoken,"");
	GetChar();
	GetBC();
	if(isalpha(ch)){
		while(isalpha(ch)||isdigit(ch)){
			Concat();
			GetChar();
		}
		Retract();
		code1=Reserve();
		if(code1==0){
			strcpy(tem.value,Insertid());
			tem.code=code1;
			return tem;}
		else {strcpy(tem.value,"-");tem.code=code1;return tem;}
	}
	else if(isdigit(ch)){
			while(isdigit(ch)){
				Concat();
				GetChar();
			}
			Retract();
			strcpy(tem.value,Insertconst());
			tem.code=7;
			return tem;
		}
	else if(ch=='='){
		tem.code=8;strcpy(tem.value,"-");return tem;}
	else if(ch=='+'){
		tem.code=9;strcpy(tem.value,"-");return tem;}
	else if(ch=='*'){
		GetChar();
		if(ch=='*'){
			tem.code=11;strcpy(tem.value,"-");return tem;}
		Retract();
		tem.code=10;strcpy(tem.value,"-");return tem;}
	else if(ch==','){
		tem.code=12;strcpy(tem.value,"-");return tem;}
	else if(ch=='('){
		tem.code=13;strcpy(tem.value,"-");return tem;}
	else if(ch==')'){
		tem.code=14;strcpy(tem.value,"-");return tem;}
	else{
		tem.code=15;strcpy(tem.value,"don't justic");return tem;}
}
void main()
{
	gets(buffer);
	struct node a;
	a=scan();
	printf("%d    %s\n",a.code,a.value);
}