yufa.cpp

这是一个编译原理的语法分析器

#include"string.h"
#include"iostream.h"
#include"stdio.h"
#include"conio.h"

#define OK 1
#define ERROR 0
#define FALSE 0
#define MAX 200
#define YES 1
#define NO 0
#define IF 2
#define ELSE 3
#define WHILE 4
#define DO 5
#define SWITCH 6
#define INT 22
#define CHAR 23
#define FLOAT 24
#define OTC 8
#define DEC 10
#define HEX 16
#define ASSIGN 20
#define SEMICOLON 21
#define AND 25
#define SUB 26
#define MUL 27
#define DIV 28
#define GT 29
#define LT 30
#define LP 31
#define RP 32
#define EQ 33
#define ID 34
#define CONST 35
#define THEN 36

int lookhead;

class word_analyse
{    int ch;
	 char code[MAX][MAX];
public:
	//word_analyse();
	int scan();
	int isletter(int ch);
	int isdigit(int ch);
	int isright(int ch);
	int iskeyword(char * ch);
	int isalpha(char * ch);
	int judge(char * ch);
	int yufa(int ch);
	int match(int ch);
	int fun_e();
	int fun_t();
	int fun_f();
	int fun_s();
	int fun_c();
};

int word_analyse::isletter(int ch)
{
	if(((ch>='a')&&(ch<='z'))||((ch>='A')&&(ch<='Z')))
		return(YES);
	else return(NO);
}

int word_analyse::isalpha(char * ch)
{
	if(((ch[0]>='a')&&(ch[0]<='z'))||((ch[0]>='A')&&(ch[0]<='Z')))
	{ cout<<"\n"<<"The ["<<ch<<"] is a identifier !"<<"\n";
	  return(YES);
	}
	else return(NO);
}

int word_analyse::isdigit(int ch)
{  if(((ch>='0')&&(ch<='9')))
	return(YES);
   else return(NO);
}

int word_analyse::isright(int ch)
{
   if(((ch>='0')&&(ch<='9'))||((ch>='a')&&(ch<='z'))
	   ||((ch>='A')&&(ch<='Z'))||(ch=='+')||(ch=='-')
	   ||(ch=='*')||(ch=='/')||(ch=='=')||(ch=='==')
	   ||(ch=='%')||(ch=='<')||(ch=='>')||(ch=='(')||(ch==')')||(ch==';'))
	    return(YES);
   else return(NO);
}

int word_analyse::iskeyword(char * ch)
{
  if((ch[0]=='i')&&(ch[1]=='n')&&(ch[2]=='t')&&(ch[3]==0))return(INT);
  if((ch[0]=='c')&&(ch[1]=='h')&&(ch[2]=='a')&&(ch[3]=='r')&&(ch[4]==0))return(CHAR);
  if((ch[0]=='f')&&(ch[1]=='l')&&(ch[2]=='o')&&(ch[3]=='a')&&(ch[4]=='t')&&(ch[5]==0))return(FLOAT);
  if((ch[0]=='i')&&(ch[1]=='f')&&(ch[2]==0))return(IF);
  if((ch[0]=='t')&&(ch[1]=='h')&&(ch[2]=='e')&&(ch[3]=='n')&&(ch[4]==0))return(THEN);
  if((ch[0]=='e')&&(ch[1]=='l')&&(ch[2]=='s')&&(ch[3]=='e')&&(ch[4]==0))return(ELSE);
  if((ch[0]=='w')&&(ch[1]=='h')&&(ch[2]=='i')&&(ch[3]=='l')&&(ch[4]=='e')&&(ch[5]==0))return(WHILE);
  if((ch[0]=='d')&&(ch[1]=='o')&&(ch[2]==0))return(DO);
  if((ch[0]=='s')&&(ch[1]=='w')&&(ch[2]=='i')&&(ch[3]=='t')&&(ch[4]=='c')&&(ch[5]=='h')&&(ch==0))return(SWITCH);
  return(ID);
}

int word_analyse::judge(char * ch)
{
     if((ch[0]=='0')&&((ch[1]>='0')&&(ch[1]<='7')))
	  {
		cout<<"\n"<<"This is a OTC number, OTC value is"<<"["<<ch<<"] !"<<"\n";
		return(OTC);
	  }
      if((ch[0]=='0')&&(ch[1]=='\0'))
	  { cout<<"\n"<<"This is a DEC number, DEC value is"<<"[0] !"<<"\n";
	    return(DEC);
	  }
	  if((ch[0]>='0')&&(ch[0]<='9')&&(ch[0]!='0'))
	  { cout<<"\n"<<"This is a DEC number, DEC value is"<<"["<<ch<<"] !"<<"\n";
	    return(DEC);
	  }
	  if((ch[0]=='0')&&(ch[1]=='x'))
	  { cout<<"\n"<<"This is a HEX number, HEX value is"<<"["<<ch<<"] !"<<"\n";
		return(HEX);
	  }
	return(OK);
}

int word_analyse::scan()
{   int i=0;
    int j=0;
	int x=1;
	ch=getc(stdin);
	while((ch==' ')||(ch==10))ch=getc(stdin);
	if((isright(ch)==NO)){ cout<<"\n"<<"ERROR"<<"\n"; return(ERROR); }
	ungetc(ch,stdin);
	while(x)
	{ ch=getc(stdin);
	 if((isletter(ch)==YES))
	 {  i=0;
	  while (isletter(ch)||isdigit(ch))
		{
			code[j][i]=ch;
			ch=getc(stdin);
			i++;
		}
		code[j][i]=0;
		ungetc(ch,stdin);
		if(ch==10)x=0;
		j++;
		return(iskeyword(code[j-1]));
	 }
     if((isdigit(ch)==YES))
	 {  i=0;
		while(isdigit(ch)||(ch=='x')||((ch>='a')&&(ch<='f')))
		{
			code[j][i]=ch;
			ch=getc(stdin);
			i++;
		}
		code[j][i]=0;
		ungetc(ch,stdin);
		j++;
		if(ch==10)x=0;
		return(judge(code[j-1]));
	 }
	if(ch==':')
	{    i=0;
	     code[j][i]=ch;
		 ch=getc(stdin);
		 if(ch=='='){ code[j][i++]=ch; code[j][i++]=0; j++; return(ASSIGN);}
	}
	switch(ch)
	   {
	   case'+':{ i=0; code[j][i]=ch; code[j][i++]=0; return(AND); }
	   case'-':{ i=0; code[j][i]=ch; code[j][i++]=0; return(SUB); }
	   case'*':{ i=0; code[j][i]=ch; code[j][i++]=0; return(MUL); }
	   case'/':{ i=0; code[j][i]=ch; code[j][i++]=0; return(DIV); }
	   case'=':{ i=0; code[j][i]=ch; code[j][i++]=0; return(EQ);  }
	   case'>':{ i=0; code[j][i]=ch; code[j][i++]=0; return(GT);  }
	   case'<':{ i=0; code[j][i]=ch; code[j][i++]=0; return(LT);  }
	   case'(':{ i=0; code[j][i]=ch; code[j][i++]=0; return(LP);  }
	   case')':{ i=0; code[j][i]=ch; code[j][i++]=0; return(RP);  }
	   case';':{ i=0; code[j][i]=ch; code[j][i++]=0; return(SEMICOLON); }
	   }
	if(ch==10)x=0;
	}
	return(OK);
}

int word_analyse::match(int ch)
{
	if(lookhead==ch)
	{
		lookhead=scan();
		return(OK);
	}
	else return(FALSE);
}

int word_analyse::fun_e()
{
	fun_t();
	if(lookhead==AND)
	{ match(AND);
	  fun_t();
	  cout<<"\t"<<"(E->E+T)"<<"\n";
	  return(OK);
	}
	if(lookhead==SUB)
	{
		match(SUB);
		fun_t();
		cout<<"\t"<<"(E->E-T)"<<"\n";
		return(OK);
	}
	if((lookhead!=AND)&&(lookhead!=SUB)){ cout<<"\t"<<"(E->T)"<<"\n"; return(OK); }
	//else { cout<<"ERROR"<<"\n"; return(ERROR); }
	return(OK);
}

int word_analyse::fun_t()
{
	fun_f();
	if(lookhead==MUL)
	{  match(MUL);
	   fun_f();
	   cout<<"\t"<<"(T->T*F)"<<"\n";
		return(OK);
	}
	if(lookhead==DIV)
	{  match(DIV);
	   fun_f();
	   cout<<"\t"<<"(T->T/F)"<<"\n";
	   return(OK);
	}
	if((lookhead!=DIV)&&(lookhead!=MUL)){ cout<<"\t"<<"(T->F)"<<"\n"; return(OK); }
    //else { cout<<"ERROR"<<"\n"; return(ERROR); }
    return(OK);
}

int word_analyse::fun_f()
{
	if(lookhead==LP)
	{
		match(LP);
		fun_e();
		match(RP);
		cout<<"\t"<<"(F->(E))"<<"\n";
		return(OK);
	}
	if(lookhead==ID){ match(ID); cout<<"\t"<<"(F->id)"<<"\n"; return(OK); }
	if(lookhead==CONST){ match(CONST); cout<<"\t"<<"(F->Const)"<<"\n"; return(OK); }
	else { cout<<"ERROR"<<"\n"; return(ERROR); }
}

int word_analyse::fun_s()
{
	if(lookhead==IF)
	{
		match(IF);
		fun_c();
		match(THEN);
		fun_s();
		cout<<"\t"<<"(S->if C then S)"<<"\n";
		return(OK);
	}
	if(lookhead==ID)
	{
		match(ID);
		match(EQ);
		fun_e();
		cout<<"\t"<<"(S->id=E)"<<"\n";
		return(OK);
	}
	if(lookhead==WHILE)
	{
		match(WHILE);
		fun_c();
		match(DO);
		fun_s();
		cout<<"\t"<<"(S->while C do S)"<<"\n";
		return(OK);
	}
	else { cout<<"ERROR"<<"\n"; return(ERROR); }
}

int word_analyse::fun_c()
{
   int c=0,d=0,i1=0,i2=0,i3=0;
   fun_e();
   if((lookhead==GT)||(lookhead==LT)||(lookhead==EQ))
     {
       d=lookhead;
       if(lookhead==GT)i1=match(GT);
       if(lookhead==LT)i2=match(LT);
       if(lookhead==EQ)i3=match(EQ);
       c=fun_e();
       if((i1==0)&&(i2==0)&&(i3==0)||(c==0)){ cout<<"ERROR"<<"\n"; return(ERROR); }
       if(d==GT){ cout<<"\t"<<"(C->E>E)"<<"\n"; return(OK); }
       if(d==LT){ cout<<"\t"<<"(C->E<E)"<<"\n"; return(OK); }
       if(d==EQ){ cout<<"\t"<<"(C->E=E)"<<"\n"; return(OK); }
   }
return(OK);
}

int main()
{
	char ch1;
	word_analyse word;
	while(ch1!='q')
	{
	
	cout<<"Please Input !"<<"\n";
	 lookhead=word.scan();
	 word.fun_s();
	 ch1=getch();
	}
	return(OK);
}