std::layout_right::mapping(3)

🎀 NAME 🎀

okay so bestie, this is the std::layout_right::mapping(3) page from the C++ Standard Libary manual, and the name situation is literally:

std::layout_right::mapping - std::layout_right::mapping

Periodt. That’s the whole NAME vibe. 💅

🦋 Synopsis 🦋

First things first, bestie — it’s defined in header <mdspan>, and it’s been around since C++23. Here’s the exact code energy:

Defined in header <mdspan>
template< class Extents >     (since C++23)
class layout_right::mapping;

okay so what does this icon actually do? The class template layout_right::mapping controls how multidimensional indices are mapped in a row-major manner to a one-dimensional value representing the offset. The mapping has stride 1 at rightmost extent and strides increase right-to-left as the products of extents. no cap, that’s the whole mapping moment. 🌈

Every specialization of mapping is a LayoutMapping and a TriviallyCopyable type which satisfies regular. it’s giving very well-behaved, tbh. 🫶

⚠️ and this part is serious: the program is ill-formed if the size of the multidimensional index space Extents() is not representable as a value of type Extents::index_type when Extents::rank_dynamic() is 0. not a vibe, fr fr. 💀

💅 Template parameters 💅

• Extents — specifies the number of dimensions, their sizes, and which are known at compile time. Must be a specialization of std::extents. 🧚

🌸 Member types 🌸

• extents_type — Extents
• index_type — extents_type::index_type
• size_type — extents_type::size_type
• rank_type — extents_type::rank_type
• layout_type — std::layout_right

🍓 Member objects 🍓

• extents_ (private) — the extents of type extents_type. (exposition-only member object*)

👑 Member functions 👑

• constructor — constructs a new mapping (public member function).
• operator= — assigns a mapping (public member function).

✨ Observers ✨

• extents — obtains the extents object (public member function).
• required_span_size — returns the required size of the mapping (public member function).
• operator() — maps multidimensional indices into an offset value (public member function).
• is_unique [static] — determines if this mapping is unique (every combination of indexes maps to a different underlying element) (public static member function).
• is_exhaustive [static] — determines if this mapping is exhaustive (every underlying element can be accessed with some combination of indexes) (public static member function).
• is_strided [static] — determines if this mapping is unique (every combination of indexes maps to a different underlying element) (public static member function).
• is_always_unique [static] — determines if this layout mapping is always unique (public static member function).
• is_always_exhaustive [static] — determines if this layout mapping is always exhaustive (public static member function).
• is_always_strided [static] — determines if this layout mapping is always strided (public static member function).
• stride — obtains the stride along the specified dimension (public member function).

👀 lowkey note: for is_strided, the page literally uses the same “unique” wording as above — I’m keeping it exactly as written, no editing, iykyk.

🔥 Non-member functions 🔥

• operator== — compares this layout mapping with other mapping (function template).
• submdspan_mapping(std::layout_right::mapping) (C++26) — calculates the mapping and data handle offset used for subdmspan (public member function).

🦋 See also 🦋

• mapping a layout mapping of layout_left (public member class template of std::layout_left)
• mapping a layout mapping of layout_stride (public member class template of std::layout_stride)

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that’s the whole page, bestie 🫶 source: http://cppreference.com · version/date: 2024.06.10 · page: std::layout_right::mapping(3) 💖✨