title: premature eof error in flex file
body: <p>I have the following code and it gives an error" "hello.l",line 31: premature EOF" when I run the following command
  flex hello.l</p>
  
  <pre><code>%{
  
    #include &lt;stdlib.h&gt;
    #include "y.tab.h"
  
    %}
  
  %%
  
  ("hi"|"oi")"\n"      {return HI; }
  ("tchau"|"bye")"\n"  {return BYE;}
  .                    {yyerror(); }
  
  %%
  
  int main(void)
  {
      yyparse();
      return 0;
  }
  
  int yywrap(void)
  {
      return 0;
  }
  
  int yyerror(void)
  {
      printf("Error\n");
      exit(1);
  }
  </code></pre>