yanboyufa.cpp

编译原理程序by me.

#include <string.h>
#include <stdio.h>
#include <string.h>
#include <iostream.h>
#include <stdlib.h>
#include <conio.h>
char *nexttoken();
void S();
void C();
void E();
void T();
void F();
char  lookahead[20];
int   code=0;
int   flag1=0;
char  chart[20][20];


  void match( char *t)
  {     //    cout<<lookahead<<"loodahead*******"<<endl;
	  //  cout<<t<<"TTTTTTTTTTTTTTTT"<<endl;
	  if(strcmp(lookahead,t)==0)
	  {         //  cout<<"+++++++++"<<endl;
		      strcpy(lookahead,nexttoken());
		 // cout<<lookahead<<endl;
	  }
	  else
	  {
		 printf("yu fa cuo wu\n");
		 exit(0);
	  }
  }
  char  *nexttoken()
  {    int flag=0;
		int ch,i=0;
		int isletter(int);
		int isdigit(int);
		int rightchar(char);
		int key(char *a);
		ch=getc(stdin);
		while ((ch==' ')||(ch==10))//10 is const
			 ch=getc(stdin);
		if(ch==-1) return(0);
	       if ((!rightchar(ch))&&(ch!=-1))
	       {
		cout<<"\nerror %c isn't in my language"<<ch;
	//	return(-1);
	}
	if (isdigit(ch)&&flag==0)
	{

		while(isdigit(ch))
		{
			chart[code][i]=ch;
			ch=getc(stdin);
			i=i+1;
		}
		chart[code][i+1]='\0';
		ungetc(ch,stdin);
		code=code+1;
		flag=1;
		i=0;
		//return(10);
	}
	if(isletter(ch)&&flag==0)
	{

		while (isletter(ch)||isdigit(ch))
		{
			chart[code][i]=ch;
			ch=getc(stdin);
			i=i+1;
		}
		chart[code][i]='\0';
		ungetc(ch,stdin);
		code=code+1;
		i=0;
		flag=1;
		//return(key(chart[code]));
	}
	/*if(ch==':')
	{
	    chart[code][i]=ch;
		code=code+1;
	ch=getc(stdin);
		/*if(ch=='=')
			return (2);
		else
			return(0);
	}*/
	if(ch=='+'&&flag==0)
	{
		chart[code][i]=ch;
		chart[code][i+1]='\0';
		code=code+1;//return (3);
		flag=1;
	}
	if(ch=='-'&&flag==0)  //return (4);
	{
		chart[code][i]=ch;
		chart[code][i+1]='\0';
		code=code+1;//return (3);
		 flag=1;
	}
	if(ch=='*'&&flag==0)  //return (5);
	{
		chart[code][i]=ch;
		chart[code][i+1]='\0';
		code=code+1;//return (3);
		 flag=1;
	}
	if(ch=='/'&&flag==0)  //return (6);
	{
		chart[code][i]=ch;
		chart[code][i+1]='\0';
		code=code+1;//return (3);
		flag=1;
	}
	if(ch=='('&&flag==0)  //return (21);
	{
		chart[code][i]=ch;
		chart[code][i+1]='\0';
		code=code+1;//return (3);
		  flag=1;
	}
	if(ch==')'&&flag==0)  //return (22);
	{
		chart[code][i]=ch;
		chart[code][i+1]='\0';
		code=code+1;//return (3);
		flag=1;
	}
	if(ch=='>'&&flag==0)  //return (23);
	{
		chart[code][i]=ch;
		chart[code][i+1]='\0';
		code=code+1;//return (3);
		flag=1;
	}
	if(ch=='<'&&flag==0)  //return (24);
	{
		chart[code][i]=ch;
		chart[code][i+1]='\0';
		code=code+1;//return (3);
		flag=1;
	}
	if(ch=='='&&flag==0)  //return (25);
	{
		chart[code][i]=ch;
		chart[code][i+1]='\0';
		code=code+1;//return (3);
		 flag=1;
	}
     if( key(chart[code-1])==1)
	    return   chart[code-1];
      else return  "id";
}

int isletter(int ch)
{
	if(((ch>='a')&&(ch<='z'))||((ch>='A')&&(ch<='Z')))
		return(1);
	else return(0);
}
int isdigit(int ch)
{
	if((ch>='0')&&(ch<='9'))
		return(1);
	else return(0);
}
int rightchar(char ch)
{  if   (((ch>='0')&&(ch<='9'))
	   ||((ch>='a')&&(ch<='z'))
	   ||((ch>='A')&&(ch<='Z'))
	   ||(ch==10)||(ch==':')||(ch=='=')
	   ||(ch=='+')||(ch=='-')||(ch=='*')||(ch=='/')
	   ||(ch=='(')||(ch==')')||(ch=='>')||(ch=='<'))
	   return(1);
	   else return(0);
}
int key(char *a)
{
  if(   (a[0]=='=')||(a[0]=='+')||(a[0]=='*')||(a[0]=='/')||(a[0]=='-')||(a[0]=='>')
	||((a[0]=='<')&&(a[1]=='=')&&(a[2]=='\0'))
	||((a[0]=='i')&&(a[1]=='f')&&(a[2]=='\0'))
	|| ((a[0]=='i')&&(a[1]=='d')&&(a[2]=='\0'))
      ||((a[0]=='t')&&(a[1]=='h')&&(a[2]=='e')&&(a[3]=='n')&&(a[4]=='\0'))
      || ((a[0]=='w')&&(a[1]=='h')&&(a[2]=='i')&&(a[3]=='l')&&(a[4]=='e')&&(a[5]=='\0'))
      ||((a[0]=='d')&&(a[1]=='o')&&(a[2]=='\0'))
      ||((a[0]=='e')&&(a[1]=='l')&&(a[2]=='s')&&(a[3]=='e')&&(a[4]=='\0'))
      )
     return 1;
     else return 0;
}

  void S()
 {
       //	  strcpy(lookahead,nexttoken());
	  if(strcmp(lookahead,"id")==0)
	  {
		  match("id");
		  match("=");
	       //	  cout<<"MMMMMMM"<<endl;
		  //strcpy(lookahead,nexttoken());
		  E();
		  printf("\t<S->id=E>\n");
	  }
	  else if(strcmp(lookahead,"if")==0)
	  {      //cout<<"IFIFIFIFIF"<<endl;
		 match("if");
		 C();
		 match("then");
	       //  cout<<"^^^^^^^^^^^"<<endl;
		 S();
		 printf("\t<if C then S>\n");
	  }
	  else if(strcmp(lookahead,"while")==0)
	  {
		  match("while");
		  C();
		  match("do");
		  S();
	  printf("\t<while C do S>\n");
	  }
	  else
	  {
		 printf("SS yu fa cuo wu\n");
		 exit(1);
	  }
  }
  void C()
  {       E();
	  //strcpy(lookahead,nexttoken());
	  if(strcmp(lookahead,">")==0)
	  {
	     match(">");
	     E();
	     printf("\t<C->E>E>\n");
	  }
	  else if(strcmp(lookahead,"<")==0)
	  {  match("<");
	     match("=");
	     E();
	     printf("\t<C->E<=E>\n");
	  }
	   else
	 {
		 printf("CC  yu fa cuo wu\n");
		 exit(1);
	 }
  }

  void E()
  {      T();
	 if(strcmp(lookahead,"+")==0)
	 {
	     match("+");
	     E();
	     printf("\t<E->E+T>\n");
	  }
	 else if(strcmp(lookahead,"-")==0)
	 {  match("-");
	     E();
	     printf("\t<E->E-T>\n");
	  }
	 /*else if(strcmp(lookahead,"#")==0)
	 {
		  printf("\t<E->T>\n");
	  }
	  else
	  {
		 printf("EE  yu fa cuo wu\n");
		 exit(1);
	  }*/
	 else
	 {
		  printf("\t<E->T>\n");
	  }

  }
  void T()
  {      F();
	if(strcmp(lookahead,"*")==0)
	 {
	     match("*");
	     T();
	     printf("\t<T->T*F>\n");
	  }
	 else if(strcmp(lookahead,"/")==0)
	 {
	     match("/");
	     T();
	     printf("\t<T->T/F>\n");
	  }
	 /*else if(strcmp(lookahead,"#")==0)
	 {
		  printf("\t<T->F>\n");
	  }
	  else
	  {
		 printf("TT  yu fa cuo wu\n");
		 exit(1);
	  }*/
	 else
	 {
		  printf("\t<T->F>\n");
	  }

  }
  void F()
  {       //flag1=1;
	//  cout<<"FFFFFFF"<<endl;
	 // cout<<lookahead<<endl;
	  if(strcmp(lookahead,"(")==0)
	  {
		  match("(");
		  E();
		 match(")");
		  printf("\t<F->(E)>\n");
	  }
	  else if(strcmp(lookahead,"id")==0)
	  {    // cout<<"**FFFFIDIDIDID"<<endl;
		match("id");
	       //	cout<<"**###########"<<endl;
		printf("\t<F->id>\n");
	  }
	else if(strcmp(lookahead,"const")==0)
	  {
	      match("const");
	      printf("\t<F->const>\n");
	  }
	  else
	  {
	      printf("FF yu fa cuo wu\n");
	      exit(1);
	  }
  }
  main()
  {        clrscr();
	   strcpy(lookahead,nexttoken());
	   S();
	   exit(1);
	   getch();
	   return 1;
  }