[mdspan.submdspan.*] Use \codeblocks instead of \itemdecl/descrs for definitions of structs strided_slice and submdspan_mapping_result

Author: burblebee

source/containers.tex

@@ -21542,20 +21542,21 @@
 increase by increments of \tcode{stride}.
 
 \indexlibraryglobal{strided_slice}%
-\begin{itemdecl}
-template<class OffsetType, class ExtentType, class StrideType>
-struct strided_slice {
-  using offset_type = OffsetType;
-  using extent_type = ExtentType;
-  using stride_type = StrideType;
-
-  [[no_unique_address]] OffsetType offset{};
-  [[no_unique_address]] ExtentType extent{};
-  [[no_unique_address]] StrideType stride{};
-};
-\end{itemdecl}
+\begin{codeblock}
+namespace std {
+  template<class OffsetType, class ExtentType, class StrideType>
+  struct strided_slice {
+    using offset_type = OffsetType;
+    using extent_type = ExtentType;
+    using stride_type = StrideType;
+
+    [[no_unique_address]] OffsetType offset{};
+    [[no_unique_address]] ExtentType extent{};
+    [[no_unique_address]] StrideType stride{};
+  };
+}
+\end{codeblock}
 
-\begin{itemdescr}
 \pnum
 \tcode{strided_slice} has the data members and special members specified above.
 It has no base classes or members other than those specified.
@@ -21570,7 +21571,6 @@
 indicates the indices \tcode{1}, \tcode{4}, \tcode{7}, and \tcode{10}.
 Indices are selected from the half-open interval \range{1}{1 + 10}.
 \end{note}
-\end{itemdescr}
 
 \rSec4[mdspan.submdspan.submdspan.mapping.result]{\tcode{submdspan_mapping_result}}
 
@@ -21579,15 +21579,16 @@
 are returned by overloads of \tcode{submdspan_mapping}.
 
 \indexlibraryglobal{submdspan_mapping_result}%
-\begin{itemdecl}
-template<class LayoutMapping>
-struct submdspan_mapping_result {
-  [[no_unique_address]] LayoutMapping mapping = LayoutMapping();
-  size_t offset{};
-};
-\end{itemdecl}
+\begin{codeblock}
+namespace std {
+  template<class LayoutMapping>
+  struct submdspan_mapping_result {
+    [[no_unique_address]] LayoutMapping mapping = LayoutMapping();
+    size_t offset{};
+  };
+}
+\end{codeblock}
 
-\begin{itemdescr}
 \pnum
 \tcode{submdspan_mapping_result} has
 the data members and special members specified above.
@@ -21596,7 +21597,6 @@
 \pnum
 \tcode{LayoutMapping} shall meet
 the layout mapping requirements\iref{mdspan.layout.policy.reqmts}.
-\end{itemdescr}
 
 \rSec4[mdspan.submdspan.helpers]{Exposition-only helpers}