Method null_predicate

expr.hh:107–110

  const char *negate;
  shared_ptr<value_expr> expr;
  null_predicate(prod *p) : bool_expr(p) {
    negate = ((d6()<4) ? "not " : "");
    expr = value_expr::factory(this);
  }
  virtual void out(std::ostream &out) {
    out << *expr << " is " << negate << "NULL";
  }