From Jason Turner

[mdspan.mdspan.cons]

C++20 → C++23 5.6 KB 167 lines
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Archived: C++20 | C++23
Markdown: C++20 | C++23
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tmp/tmpblvqo8me/{from.md → to.md} RENAMED
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+ ##### Constructors <a id="mdspan.mdspan.cons">[[mdspan.mdspan.cons]]</a>
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+
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+ ``` cpp
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+ constexpr mdspan();
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+ ```
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+
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+ *Constraints:*
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+
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+ - `rank_dynamic() > 0` is `true`.
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+ - `is_default_constructible_v<data_handle_type>` is `true`.
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+ - `is_default_constructible_v<mapping_type>` is `true`.
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+ - `is_default_constructible_v<accessor_type>` is `true`.
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+
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+ *Preconditions:* $[0, \texttt{\textit{map_}.required_span_size()})$ is
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+ an accessible range of *ptr\_* and *acc\_* for the values of *map\_* and
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+ *acc\_* after the invocation of this constructor.
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+
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+ *Effects:* Value-initializes *ptr\_*, *map\_*, and *acc\_*.
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+
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+ ``` cpp
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+ template<class... OtherIndexTypes>
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+ constexpr explicit mdspan(data_handle_type p, OtherIndexTypes... exts);
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+ ```
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+
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+ Let `N` be `sizeof...(OtherIndexTypes)`.
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+
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+ *Constraints:*
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+
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+ - `(is_convertible_v<OtherIndexTypes, index_type> && ...)` is `true`,
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+ - `(is_nothrow_constructible<index_type, OtherIndexTypes> && ...)` is
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+ `true`,
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+ - `N == rank() || N == rank_dynamic()` is `true`,
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+ - `is_constructible_v<mapping_type, extents_type>` is `true`, and
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+ - `is_default_constructible_v<accessor_type>` is `true`.
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+
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+ *Preconditions:* $[0, \texttt{\textit{map_}.required_span_size()})$ is
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+ an accessible range of `p` and *acc\_* for the values of *map\_* and
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+ *acc\_* after the invocation of this constructor.
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+
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+ *Effects:*
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+
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+ - Direct-non-list-initializes *ptr\_* with `std::move(p)`,
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+ - direct-non-list-initializes *map\_* with
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+ `extents_type(static_cast<index_type>(std::move(exts))...)`, and
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+ - value-initializes *acc\_*.
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+
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+ ``` cpp
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+ template<class OtherIndexType, size_t N>
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+ constexpr explicit(N != rank_dynamic())
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+ mdspan(data_handle_type p, span<OtherIndexType, N> exts);
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+ template<class OtherIndexType, size_t N>
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+ constexpr explicit(N != rank_dynamic())
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+ mdspan(data_handle_type p, const array<OtherIndexType, N>& exts);
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+ ```
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+
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+ *Constraints:*
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+
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+ - `is_convertible_v<const OtherIndexType&, index_type>` is `true`,
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+ - `(is_nothrow_constructible<index_type, const OtherIndexType&> && ...)`
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+ is `true`,
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+ - `N == rank() || N == rank_dynamic()` is `true`,
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+ - `is_constructible_v<mapping_type, extents_type>` is `true`, and
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+ - `is_default_constructible_v<accessor_type>` is `true`.
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+
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+ *Preconditions:* $[0, \texttt{\textit{map_}.required_span_size()})$ is
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+ an accessible range of `p` and *acc\_* for the values of *map\_* and
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+ *acc\_* after the invocation of this constructor.
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+
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+ *Effects:*
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+
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+ - Direct-non-list-initializes *ptr\_* with `std::move(p)`,
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+ - direct-non-list-initializes *map\_* with `extents_type(exts)`, and
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+ - value-initializes *acc\_*.
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+
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+ ``` cpp
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+ constexpr mdspan(data_handle_type p, const extents_type& ext);
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+ ```
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+
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+ *Constraints:*
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+
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+ - `is_constructible_v<mapping_type, const extents_type&>` is `true`, and
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+ - `is_default_constructible_v<accessor_type>` is `true`.
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+
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+ *Preconditions:* $[0, \texttt{\textit{map_}.required_span_size()})$ is
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+ an accessible range of `p` and *acc\_* for the values of *map\_* and
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+ *acc\_* after the invocation of this constructor.
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+
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+ *Effects:*
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+
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+ - Direct-non-list-initializes *ptr\_* with `std::move(p)`,
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+ - direct-non-list-initializes *map\_* with `ext`, and
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+ - value-initializes *acc\_*.
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+
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+ ``` cpp
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+ constexpr mdspan(data_handle_type p, const mapping_type& m);
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+ ```
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+
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+ *Constraints:* `is_default_constructible_v<accessor_type>` is `true`.
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+
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+ *Preconditions:* [0, `m.required_span_size()`) is an accessible range of
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+ `p` and *acc\_* for the value of *acc\_* after the invocation of this
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+ constructor.
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+
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+ *Effects:*
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+
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+ - Direct-non-list-initializes *ptr\_* with `std::move(p)`,
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+ - direct-non-list-initializes *map\_* with `m`, and
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+ - value-initializes *acc\_*.
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+
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+ ``` cpp
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+ constexpr mdspan(data_handle_type p, const mapping_type& m, const accessor_type& a);
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+ ```
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+
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+ *Preconditions:* [0, `m.required_span_size()`) is an accessible range of
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+ `p` and `a`.
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+
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+ *Effects:*
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+
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+ - Direct-non-list-initializes *ptr\_* with `std::move(p)`,
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+ - direct-non-list-initializes *map\_* with `m`, and
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+ - direct-non-list-initializes *acc\_* with `a`.
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+
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+ ``` cpp
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+ template<class OtherElementType, class OtherExtents,
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+ class OtherLayoutPolicy, class OtherAccessor>
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+ constexpr explicit(see below)
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+ mdspan(const mdspan<OtherElementType, OtherExtents,
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+ OtherLayoutPolicy, OtherAccessor>& other);
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+ ```
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+
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+ *Constraints:*
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+
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+ - `is_constructible_v<mapping_type, const OtherLayoutPolicy::template mapping<Oth- erExtents>&>`
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+ is `true`, and
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+ - `is_constructible_v<accessor_type, const OtherAccessor&>` is `true`.
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+
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+ *Mandates:*
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+
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+ - `is_constructible_v<data_handle_type, const OtherAccessor::data_handle_type&>`
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+ is `true`, and
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+ - `is_constructible_v<extents_type, OtherExtents>` is `true`.
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+
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+ *Preconditions:*
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+
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+ - For each rank index `r` of `extents_type`,
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+ `static_extent(r) == dynamic_extent || static_extent(r) == other.extent(r)`
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+ is `true`.
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+ - $[0, \texttt{\textit{map_}.required_span_size()})$ is an accessible
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+ range of *ptr\_* and *acc\_* for values of *ptr\_*, *map\_*, and
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+ *acc\_* after the invocation of this constructor.
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+
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+ *Effects:*
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+
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+ - Direct-non-list-initializes *ptr\_* with `other.`*`ptr_`*,
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+ - direct-non-list-initializes *map\_* with `other.`*`map_`*, and
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+ - direct-non-list-initializes *acc\_* with `other.`*`acc_`*.
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+
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+ *Remarks:* The expression inside `explicit` is equivalent to:
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+
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+ ``` cpp
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+ !is_convertible_v<const OtherLayoutPolicy::template mapping<OtherExtents>&, mapping_type>
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+ || !is_convertible_v<const OtherAccessor&, accessor_type>
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+ ```
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+