added code to print out positions of incorrect tokens

runner.c

@@ -79,6 +79,9 @@ int run(FILE *alpha) {
             }
             continue;
 	}
+   	if(token == 1999){
+                printf("On line number %d and column number %d we have an invalid character:%s\n",line_number,column_number,yytext);
+                }
 	column_number += yyleng;
     }