漂亮可打印的标准::正则表达式

Question

我希望能够打印正则表达式。出于正当理由，std::regex没有保留文本正则表达式的副本，因此我们必须自己包装它。然而，简单的聚合非常冗长。有推荐的做法吗？如下所述，公共继承是否存在令人讨厌的问题？

#include <iomanip>
#include <iostream>
#include <string>
#include <regex>

template <
  class CharT,
  class Traits = std::regex_traits<CharT>
  >
class basic_pp_regex
  : public std::basic_regex<CharT, Traits>
{
public:
  using self = basic_pp_regex;
  using super = std::basic_regex<CharT, Traits>;

  template <typename... Args>
  basic_pp_regex(std::string pretty, Args&&... args)
    : super{pretty, std::forward<Args>(args)...}
    , _pretty{std::move(pretty)}
  {}

  basic_pp_regex(basic_pp_regex const&) = default;
  basic_pp_regex(basic_pp_regex&&) = default;
  // The default regex matches nothing.
  basic_pp_regex()
    : basic_pp_regex{"$."}
  {}

  friend
  std::ostream& operator<<(std::ostream& o, self const& s)
  {
    return o << std::quoted(s._pretty, '/');
  }

private:
  std::string _pretty;
};

using pp_regex = basic_pp_regex<char>;

int main()
{
  auto re = pp_regex("/foo");
  auto s = "/root/foo/bar";
  std::cout << s << " ~ " << re << " =  " << std::regex_search(s, re) << '\n';
}

给出：

/root/foo/bar ~ /\/foo/ =  1