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cppdraft/func/wrap/general.md

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+[func.wrap.general]
+
+# 22 General utilities library [[utilities]](./#utilities)
+
+## 22.10 Function objects [[function.objects]](function.objects#func.wrap.general)
+
+### 22.10.17 Polymorphic function wrappers [[func.wrap]](func.wrap#general)
+
+#### 22.10.17.1 General [func.wrap.general]
+
+[1](#1)
+
+[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/utilities.tex#L13594)
+
+Subclause [[func.wrap]](func.wrap "22.10.17 Polymorphic function wrappers") describes polymorphic wrapper classes that
+encapsulate arbitrary callable objects[.](#1.sentence-1)
+
+[2](#2)
+
+[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/utilities.tex#L13598)
+
+Let t be an object of a type that is a specialization offunction, copyable_function, or move_only_function,
+such that the target object x of t has a type that
+is a specialization offunction, copyable_function, or move_only_function[.](#2.sentence-1)
+
+Each argument of the
+invocation of x evaluated as part of the invocation of t may alias an argument in the same position in the invocation of t that
+has the same type, even if the corresponding parameter is not of reference type[.](#2.sentence-2)
+
+[*Example [1](#example-1)*: move_only_function<void(T)> f{copyable_function<void(T)>{[](T) {}}};
+T t;
+f(t); // it is unspecified how many copies of T are made — *end example*]
+
+[3](#3)
+
+[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/utilities.tex#L13616)
+
+*Recommended practice*: Implementations should avoid double wrapping when
+constructing polymorphic wrappers from one another[.](#3.sentence-1)