Class custom_axis

test/histogram_test.cpp:655–664

  // custom axis
  {
    struct custom_axis : public axis::integer<> {
      using value_type = const char*; // type that is fed to the axis

      using integer::integer; // inherit ctors of base

      // the customization point
      // - accept const char* and convert to int
      // - then call index method of base class
      int index(value_type s) const { return integer::index(std::atoi(s)); }
    };

    auto h = make(Tag(), custom_axis(0, 3));
    h("-10");