Lambda Expressions (C++11)

In a Nutshell

Lambdas allow us to define an anonymous function object directly in code. They are commonly used to pass short snippets of logic as arguments to algorithms or callbacks.

Header

None (language feature)

Core API Quick Reference

Operation	Signature	Description
No-capture lambda	[]() {}	Basic syntax, generates a closure type
No-argument lambda	[] {}	Shorthand omitting the parameter list
Capture by value	[x]	Captures variables by copying their value
Capture by reference	[&x]	Captures variables by reference
Capture all by value	[=]	Captures all used automatic variables by value
Capture all by reference	[&]	Captures all used automatic variables by reference
Mutable lambda	[x]() mutable	Allows modification of the captured copy
Generic lambda	[[](auto x)	Parameters use auto, templated operator()
Explicit template parameters	[]<typename T>(T x)	C++20, explicitly specifies template parameter list
Static lambda	[]() static	C++23, operator() is a static member function

Minimal Example

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

int main() {
    std::vector<int> v{3, 1, 4, 1, 5, 9};

    // Define a lambda to check if a number is even
    auto is_even = [](int n) { return n % 2 == 0; };

    // Use it with an algorithm
    auto count = std::count_if(v.begin(), v.end(), is_even);

    std::cout << "Even numbers: " << count << std::endl;
    return 0;
}

Embedded Suitability: High

• Closure types are generated at compile time with no heap allocation overhead and zero additional runtime cost.
• Replaces function pointers and raw functors, making callback code more compact and readable.
• Be aware of lifetime risks with reference captures in asynchronous or interrupt contexts; value capture is recommended for embedded callbacks.
• C++14 generic lambdas allow us to write generic sorting/searching comparison logic without template overhead.

Compiler Support

GCC	Clang	MSVC
4.5	3.1	19.0

See Also

• cppreference: Lambda expressions

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