std::default_accessor(3)

🌸 NAME 🌸

std::default_accessor — bestie, this is the default accessor, the fallback queen of <mdspan> 💅 (and yes, this page lives in the C++ Standard Library manual, section 3, iykyk)

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✨ Synopsis ✨

Okay so picture this: it's defined in the header <mdspan>, right, and it looks like this:

template< class ElementType >  (since C++23)
class default_accessor;

The std::default_accessor class template is literally the default AccessorPolicy that std::mdspan uses when you don't hand it a user-specified accessor policy of your own. It's the "no thoughts, just vibes" of accessor policies, and honestly? It ate. 🫶

Every single specialization of default_accessor models semiregular and is TriviallyCopyable. Periodt. ✨

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🦋 Template parameters 🦋

• ElementType — the element type, bestie. It shall be a complete object type that is neither an abstract class type nor an array type. Otherwise? The program is ill-formed. 💀 Like, not "oopsie" ill-formed, we're talking hard no. Respect the rules.

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🎀 Member types 🎀

Here's the whole cast, main character energy only:

• offset_policy — default_accessor
• element_type — ElementType
• reference — ElementType&
• data_handle_type — ElementType*

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💜 Member functions 💜

• constructor — constructs a default_accessor (public member function)
• access — returns the *n*th element provided by arguments (public member function)
• offset — returns a data handle that has an offset provided by arguments (public member function)

🌈 std::default_accessor::default_accessor

Behold, the constructors:

constexpr default_accessor() noexcept = default;       (1)

template< class OtherElementType >
constexpr default_accessor( default_accessor<OtherElementType> ) noexcept {}   (2)

1. Default constructs a default_accessor. Iconic, effortless, no notes. 💅
2. Constructs a default_accessor from default_accessor<OtherElementType>. The constructor has no visible effect — literally does nothing visible, it's giving "showed up, served looks, said nothing" 😭. This overload participates in overload resolution only if std::is_convertible_v<OtherElementType(*)[], element_type(*)[]> is true. That's the whole vibe check, no cap.

💖 std::default_accessor::access

constexpr reference access( data_handle_type p, std::size_t i ) const noexcept;

Equivalent to return p[i];. That's it. That's the function. Simple, clean, slays. ✨

🍓 std::default_accessor::offset

constexpr data_handle_type offset( data_handle_type p, std::size_t i ) const noexcept;

Equivalent to return p + i;. Pointer math but make it fashion. 🧚

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🙈 Example

This section is incomplete.

Reason: no example 😭

It's giving "left on read". The example section is literally Todo no example — big mood, honestly.

Category:

• Todo no example

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And that's the tea, bestie 🫶💖 — this page came to you courtesy of cppreference.com, dated 2024.06.10, on the std::default_accessor(3) page of the C++ Standard Library manual. Go forth and accessor, queen 👑✨