%{
    /* some initial C programs */
#define BEGINSYM 1
#define INTEGER  2
#define IDNAME   3
#define REAL     4
#define STRING   5
#define SEMICOLONSYM 6
#define ASSIGNSYM 7
%}
Digit       [0-9]
Letter      [a-zA-Z]
IntLit      {Digit}+
Id          {Letter}({Letter}|{Digit}|_)*
%%
[ \t\n] {/* skip white spaces */}
[Bb][Ee][Gg][Ii][Nn]              {return(BEGINSYM);}
{IntLit}                          {return(INTEGER);}
{Id}             {
                  printf("var has %d characters, ",yyleng);
                  return(IDNAME);
                 }
({IntLit}[.]{IntLit})([Ee][+-]?{IntLit})? {return(REAL);}
\"[^\"\n]*\"   {stripquotes(); return(STRING);}
";"                               {return(SEMICOLONSYM);}
":="                              {return(ASSIGNSYM);}
.         {printf("error --- %s\n",yytext);}
%%
/* some final C programs */
stripquotes()
{
  /* handling string within a quoted string */
  int frompos, topos=0, numquotes = 2;
  for(frompos=1; frompos<yyleng; frompos++){
    yytext[topos++] = yytext[frompos];
  }
  yyleng -= numquotes;
  yytext[yyleng] = '\0';
}
void main(){
  int i;

  i =  yylex();
  while(i>0 && i < 8){
    printf("<%s> is %d\n",yytext,i);
    i =  yylex();
  }
}