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cppdraft/span/sub.md

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+[span.sub]
+
+# 23 Containers library [[containers]](./#containers)
+
+## 23.7 Views [[views]](views#span.sub)
+
+### 23.7.2 Contiguous access [[views.contiguous]](views.contiguous#span.sub)
+
+#### 23.7.2.2 Class template span [[views.span]](views.span#span.sub)
+
+#### 23.7.2.2.4 Subviews [span.sub]
+
+[🔗](#lib:span,first)
+
+`template<size_t Count> constexpr span<element_type, Count> first() const;
+`
+
+[1](#1)
+
+[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/containers.tex#L20640)
+
+*Mandates*: Count <= Extent is true[.](#1.sentence-1)
+
+[2](#2)
+
+[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/containers.tex#L20644)
+
+*Hardened preconditions*: Count <= size() is true[.](#2.sentence-1)
+
+[3](#3)
+
+[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/containers.tex#L20648)
+
+*Effects*: Equivalent to: return R{data(), Count}; where R is the return type[.](#3.sentence-1)
+
+[🔗](#lib:span,last)
+
+`template<size_t Count> constexpr span<element_type, Count> last() const;
+`
+
+[4](#4)
+
+[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/containers.tex#L20660)
+
+*Mandates*: Count <= Extent is true[.](#4.sentence-1)
+
+[5](#5)
+
+[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/containers.tex#L20664)
+
+*Hardened preconditions*: Count <= size() is true[.](#5.sentence-1)
+
+[6](#6)
+
+[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/containers.tex#L20668)
+
+*Effects*: Equivalent to: return R{data() + (size() - Count), Count}; where R is the return type[.](#6.sentence-1)
+
+[🔗](#lib:span,subspan)
+
+`template<size_t Offset, size_t Count = dynamic_extent>
+  constexpr span<element_type, see below> subspan() const;
+`
+
+[7](#7)
+
+[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/containers.tex#L20681)
+
+*Mandates*: Offset <= Extent && (Count == dynamic_extent || Count <= Extent - Offset) is true[.](#7.sentence-1)
+
+[8](#8)
+
+[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/containers.tex#L20688)
+
+*Hardened preconditions*: Offset <= size() && (Count == dynamic_extent || Count <= size() - Offset) is true[.](#8.sentence-1)
+
+[9](#9)
+
+[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/containers.tex#L20695)
+
+*Effects*: Equivalent to:return span<ElementType, *see below*>( data() + Offset, Count != dynamic_extent ? Count : size() - Offset);
+
+[10](#10)
+
+[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/containers.tex#L20703)
+
+*Remarks*: The second template argument of the returned span type is:Count != dynamic_extent ? Count : (Extent != dynamic_extent ? Extent - Offset : dynamic_extent)
+
+[🔗](#lib:span,first_)
+
+`constexpr span<element_type, dynamic_extent> first(size_type count) const;
+`
+
+[11](#11)
+
+[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/containers.tex#L20719)
+
+*Hardened preconditions*: count <= size() is true[.](#11.sentence-1)
+
+[12](#12)
+
+[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/containers.tex#L20723)
+
+*Effects*: Equivalent to: return {data(), count};
+
+[🔗](#lib:span,last_)
+
+`constexpr span<element_type, dynamic_extent> last(size_type count) const;
+`
+
+[13](#13)
+
+[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/containers.tex#L20734)
+
+*Hardened preconditions*: count <= size() is true[.](#13.sentence-1)
+
+[14](#14)
+
+[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/containers.tex#L20738)
+
+*Effects*: Equivalent to: return {data() + (size() - count), count};
+
+[🔗](#lib:span,subspan_)
+
+`constexpr span<element_type, dynamic_extent> subspan(
+  size_type offset, size_type count = dynamic_extent) const;
+`
+
+[15](#15)
+
+[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/containers.tex#L20750)
+
+*Hardened preconditions*: offset <= size() && (count == dynamic_extent || count <= size() - offset) is true[.](#15.sentence-1)
+
+[16](#16)
+
+[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/containers.tex#L20757)
+
+*Effects*: Equivalent to:return {data() + offset, count == dynamic_extent ? size() - offset : count};