Generic Lambdas (C++14)

In a Nutshell

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

Header

None (language feature)

Core API Quick Reference

Operation	Signature	Description
Generic parameters	[](auto x) {}	Use auto to declare parameters; generates a templated operator() based on deduced types
Forwarding reference parameters	[](auto&& x) {}	Combine with std::forward to perfectly forward parameter packs
Explicit template parameters (C++20)	[]<typename T>(T x) {}	Explicitly declare template parameters using angle brackets after the square brackets; supports constraints
No-capture function pointer conversion	[](auto x) {}	No-capture generic lambdas can be implicitly converted to function pointers (since C++17, constexpr)

Minimal Example

#include <algorithm>
#include <vector>
#include <iostream>

int main() {
    std::vector<int> v{5, 2, 8, 1, 9};

    // Generic lambda: works with int, double, or custom types supporting comparison
    auto greater = [](auto a, auto b) {
        return a > b;
    };

    // Sort in descending order
    std::sort(v.begin(), v.end(), greater);

    for (const auto& x : v) {
        std::cout << x << " ";
    }
    // Output: 9 8 5 2 1
}

Embedded Applicability: High

• Zero runtime overhead; auto is deduced at compile-time only, and the generated code is identical to hand-written templates.
• Ideal for writing generic callback functions (e.g., sorting comparators, timer callbacks), reducing template code redundancy.
• The C++14 auto syntax is widely supported by GCC 5+ and Clang 3.4+, making it usable with mainstream embedded toolchains.

Compiler Support

GCC	Clang	MSVC
5.0	3.4	19.0

See Also

• cppreference: Lambda expressions

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