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cppdraft/optional/nullopt.md

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+[optional.nullopt]
+
+# 22 General utilities library [[utilities]](./#utilities)
+
+## 22.5 Optional objects [[optional]](optional#nullopt)
+
+### 22.5.5 No-value state indicator [optional.nullopt]
+
+[🔗](#lib:nullopt_t)
+
+`struct nullopt_t{see below};
+inline constexpr nullopt_t nullopt(unspecified);
+`
+
+[1](#1)
+
+[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/utilities.tex#L4998)
+
+The struct nullopt_t is an empty class type used as a unique type to indicate the state of not containing a value for optional objects[.](#1.sentence-1)
+
+In particular, optional<T> has a constructor with nullopt_t as a single argument;
+this indicates that an optional object not containing a value shall be constructed[.](#1.sentence-2)
+
+[2](#2)
+
+[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/utilities.tex#L5003)
+
+Type nullopt_t shall not have a default constructor or an initializer-list constructor, and shall not be an aggregate[.](#2.sentence-1)