Comments on: Clearer interfaces with optional<T> https://www.fluentcpp.com/2016/11/24/clearer-interfaces-with-optionalt/ Jonathan Boccara's blog Tue, 06 Nov 2018 00:41:00 +0000 hourly 1 https://wordpress.org/?v=6.5.4 By: 🐾vorpal🐾 https://www.fluentcpp.com/2016/11/24/clearer-interfaces-with-optionalt/#comment-1440 Tue, 06 Nov 2018 00:41:00 +0000 https://www.fluentcpp.com/?p=72#comment-1440 Also, the implementations seem… bizarre? In clang, I’m having trouble figuring out why they chose the implementation they did:


struct nullopt_t
{
    struct __secret_tag { _LIBCPP_INLINE_VISIBILITY explicit __secret_tag() = default; };
    _LIBCPP_INLINE_VISIBILITY constexpr explicit nullopt_t(__secret_tag, __secret_tag) noexcept {}
};

_LIBCPP_INLINE_VAR constexpr nullopt_t nullopt{nullopt_t::__secret_tag{}, nullopt_t::__secret_tag{}};

Why the double __secret_tag (which isn’t really at all secret, anyway)?

GCC has a single tag that at least seems to make more sense.

]]> By: 🐾vorpal🐾 https://www.fluentcpp.com/2016/11/24/clearer-interfaces-with-optionalt/#comment-1439 Tue, 06 Nov 2018 00:27:00 +0000 https://www.fluentcpp.com/?p=72#comment-1439 I’m really surprised that they didn’t implement std::optional with an iterator so that you could use it in most STL functions. It seems pretty stunted compared to the equivalent of optional in other languages: it would be nice to be able to filter and map over optionals, for example, as if they were lists of length 0 / 1.

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