std::layout...ide::mapping(3)

💅 NAME 💅

std::layout_stride::mapping — literally the mapping class for std::layout_stride, bestie

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✨ Synopsis ✨

Okay so first things first, this whole situation lives in the header <mdspan> 🫶

template< class Extents >      (since C++23)
class layout_stride::mapping;

So the class template layout_stride::mapping is the main character that controls how multidimensional indices get mapped — using user-defined strides, no less — onto a one-dimensional value that represents the offset. Slay.

Every single specialization of mapping is a LayoutMapping and a TriviallyCopyable type, and it also satisfies regular. Like, it's giving well-behaved, honestly.

🚨 Real talk though: the program is ill-formed if the size of the multidimensional index space Extents() isn't representable as a value of type Extents::index_type when Extents::rank_dynamic() is 0. So watch out for that, okay? Not a drill.

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🌸 Template parameters 🌸

• Extents — specifies the number of dimensions, their sizes, and which ones are known at compile time. Has to be a specialization of std::extents, no exceptions. 💖

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🎀 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_stride

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🦋 Member constants 🦋

• constexpr rank_type rank_ (private) — extents_type::rank(). Also flagged [static] — it's an *exposition-only static member constant**. iykyk ✨

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🌈 Member objects 🌈

• extents_ (private) — the extents, of type extents_type. (exposition-only member object*)
• strides_ (private) — the strides, of type std::array<index_type, rank_>. (exposition-only member object*)

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👑 Member functions 👑

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

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💜 Observers 💜

• extents — obtains the extents object (public member function)
• strides — obtains the array of strides (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 — determines if this mapping is exhaustive (every underlying element can be accessed with some combination of indexes) (public 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)

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🧚 Non-member functions 🧚

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

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🍓 See also 🍓

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

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and that's the whole vibe, bestie ✨💖 This little beauty comes to you from http://cppreference.com, dated 2024.06.10 — std::layout...ide::mapping(3), periodt. 🎀