Listing 1

ret = yylex();
switch(ret)
   {
case SET:
   /* Next input should be the numeric value */
   ret = yylex();
   if (ret != INTEGER_NUMBER)
      {
      printf("\n ERROR -- number not specified
            after SET");
      exit(0);
      }
   else
      sscanf(yytext,"%d",&value);
   break;
   ...