Editing Template (C++) (section)

==== Abbreviated function templates ====
Since [[C++20]], using <code>auto</code> or <code>[[concepts (C++)|Concept]] auto</code> in any of the parameters of a [[function declaration]], that declaration becomes an ''abbreviated function template'' declaration.<ref>{{cite web|url=http://open-std.org/JTC1/SC22/WG21/docs/papers/2018/p1141r1.html|title=P1141R1 - Yet another approach for constrained declarations|access-date=2018-11-11|archive-date=2018-11-11|archive-url=https://web.archive.org/web/20181111133625/http://open-std.org/JTC1/SC22/WG21/docs/papers/2018/p1141r1.html|url-status=live}}</ref> Such a declaration declares a function template and one invented template parameter for each placeholder is appended to the template parameter list:
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void f1(auto); // same as template<class T> void f1(T)
void f2(C1 auto); // same as template<C1 T> void f2(T), if C1 is a concept
void f3(C2 auto...); // same as template<C2... Ts> void f3(Ts...), if C2 is a concept
void f4(C2 auto, ...); // same as template<C2 T> void f4(T...), if C2 is a concept
void f5(const C3 auto*, C4 auto&); // same as template<C3 T, C4 U> void f5(const T*, U&);
</syntaxhighlight>