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+[optional.monadic]
+
+# 22 General utilities library [[utilities]](./#utilities)
+
+## 22.5 Optional objects [[optional]](optional#monadic)
+
+### 22.5.3 Class template optional [[optional.optional]](optional.optional#optional.monadic)
+
+#### 22.5.3.8 Monadic operations [optional.monadic]
+
+[ð](#lib:and_then,optional)
+
+`template<class F> constexpr auto and_then(F&& f) &;
+template<class F> constexpr auto and_then(F&& f) const &;
+`
+
+[1](#1)
+
+[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/utilities.tex#L4266)
+
+Let U be invoke_result_t<F, decltype(**val*)>[.](#1.sentence-1)
+
+[2](#2)
+
+[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/utilities.tex#L4269)
+
+*Mandates*: remove_cvref_t<U> is a specialization of optional[.](#2.sentence-1)
+
+[3](#3)
+
+[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/utilities.tex#L4273)
+
+*Effects*: Equivalent to:if (*this) {return invoke(std::forward<F>(f), **val*);} else {return remove_cvref_t<U>();}
+
+[ð](#lib:and_then,optional_)
+
+`template<class F> constexpr auto and_then(F&& f) &&;
+template<class F> constexpr auto and_then(F&& f) const &&;
+`
+
+[4](#4)
+
+[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/utilities.tex#L4292)
+
+Let U be invoke_result_t<F, decltype(std::move(**val*))>[.](#4.sentence-1)
+
+[5](#5)
+
+[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/utilities.tex#L4295)
+
+*Mandates*: remove_cvref_t<U> is a specialization of optional[.](#5.sentence-1)
+
+[6](#6)
+
+[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/utilities.tex#L4299)
+
+*Effects*: Equivalent to:if (*this) {return invoke(std::forward<F>(f), std::move(**val*));} else {return remove_cvref_t<U>();}
+
+[ð](#lib:transform,optional)
+
+`template<class F> constexpr auto transform(F&& f) &;
+template<class F> constexpr auto transform(F&& f) const &;
+`
+
+[7](#7)
+
+[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/utilities.tex#L4318)
+
+Let U be remove_cv_t<invoke_result_t<F, decltype(**val*)>>[.](#7.sentence-1)
+
+[8](#8)
+
+[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/utilities.tex#L4321)
+
+*Mandates*: U is a valid contained type for optional[.](#8.sentence-1)
+
+The declarationU u(invoke(std::forward<F>(f), **val*)); is well-formed for some invented variable u[.](#8.sentence-2)
+
+[*Note [1](#note-1)*:
+
+There is no requirement that U is movable ([[dcl.init.general]](dcl.init.general "9.5.1 General"))[.](#8.sentence-3)
+
+â *end note*]
+
+[9](#9)
+
+[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/utilities.tex#L4333)
+
+*Returns*: If *this contains a value, an optional<U> object
+whose contained value is direct-non-list-initialized withinvoke(std::forward<F>(f), **val*);
+otherwise, optional<U>()[.](#9.sentence-1)
+
+[ð](#lib:transform,optional_)
+
+`template<class F> constexpr auto transform(F&& f) &&;
+template<class F> constexpr auto transform(F&& f) const &&;
+`
+
+[10](#10)
+
+[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/utilities.tex#L4348)
+
+Let U beremove_cv_t<invoke_result_t<F, decltype(std::move(**val*))>>[.](#10.sentence-1)
+
+[11](#11)
+
+[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/utilities.tex#L4352)
+
+*Mandates*: U is a valid contained type for optional[.](#11.sentence-1)
+
+The declarationU u(invoke(std::forward<F>(f), std::move(**val*))); is well-formed for some invented variable u[.](#11.sentence-2)
+
+[*Note [2](#note-2)*:
+
+There is no requirement that U is movable ([[dcl.init.general]](dcl.init.general "9.5.1 General"))[.](#11.sentence-3)
+
+â *end note*]
+
+[12](#12)
+
+[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/utilities.tex#L4364)
+
+*Returns*: If *this contains a value, an optional<U> object
+whose contained value is direct-non-list-initialized withinvoke(std::forward<F>(f), std::move(**val*));
+otherwise, optional<U>()[.](#12.sentence-1)
+
+[ð](#lib:or_else,optional)
+
+`template<class F> constexpr optional or_else(F&& f) const &;
+`
+
+[13](#13)
+
+[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/utilities.tex#L4378)
+
+*Constraints*: F models [invocable](concept.invocable#concept:invocable "18.7.2 Concept invocable [concept.invocable]") andT models [copy_constructible](concept.copyconstructible#concept:copy_constructible "18.4.14 Concept copy_constructible [concept.copyconstructible]")[.](#13.sentence-1)
+
+[14](#14)
+
+[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/utilities.tex#L4383)
+
+*Mandates*: is_same_v<remove_cvref_t<invoke_result_t<F>>, optional> is true[.](#14.sentence-1)
+
+[15](#15)
+
+[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/utilities.tex#L4387)
+
+*Effects*: Equivalent to:if (*this) {return *this;} else {return std::forward<F>(f)();}
+
+[ð](#lib:or_else,optional_)
+
+`template<class F> constexpr optional or_else(F&& f) &&;
+`
+
+[16](#16)
+
+[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/utilities.tex#L4405)
+
+*Constraints*: F models [invocable](concept.invocable#concept:invocable "18.7.2 Concept invocable [concept.invocable]") andT models [move_constructible](concept.moveconstructible#concept:move_constructible "18.4.13 Concept move_constructible [concept.moveconstructible]")[.](#16.sentence-1)
+
+[17](#17)
+
+[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/utilities.tex#L4410)
+
+*Mandates*: is_same_v<remove_cvref_t<invoke_result_t<F>>, optional> is true[.](#17.sentence-1)
+
+[18](#18)
+
+[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/utilities.tex#L4414)
+
+*Effects*: Equivalent to:if (*this) {return std::move(*this);} else {return std::forward<F>(f)();}