Generic Lambda (C++14)

In a Nutshell

Allows lambda expression parameters to support auto, eliminating the hassle of writing multiple overloads for different types. It is equivalent to generating a templated operator().

Header

None (language feature)

Quick API Reference

Operation	Signature	Description
Generic parameter	[captures](auto a, auto b) { ... }	Declares parameters using auto, generating a template operator() based on deduced types
Forwarding reference parameter	[captures](auto&&... ts) { ... }	Combines with auto&& to perfectly forward parameter packs
Explicit template parameters (C++20)	[captures]<class T>(T a) { ... }	Explicitly declares template parameters using angle brackets after square brackets, supporting constraints
Captureless conversion to function pointer	using F = ret(*)(params); operator F() const;	A captureless generic lambda can implicitly convert to a function pointer (constexpr since C++17)

Minimal Example

#include <iostream>
// Standard: C++14
int main() {
    auto compare = [](auto a, auto b) { return a < b; };
    std::cout << compare(3, 4) << "\n";       // int vs int
    std::cout << compare(3.14, 2.72) << "\n"; // double vs double
}

Embedded Applicability: High

• Zero runtime overhead; auto is deduced only at compile time, and the generated code is identical to hand-written templates
• Ideal for writing generic callback functions (such as sort comparators, timer callbacks), reducing template code redundancy
• The C++14 auto syntax is widely supported by GCC 5+ / Clang 3.4+, and can be used with mainstream embedded toolchains

Compiler Support

GCC	Clang	MSVC
5.0	3.4	19.0

See Also

• cppreference: Lambda expressions

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