Lambda Expressions (C++11)

In a Nutshell

A lambda lets us define an anonymous function object in-place right in our code, and is 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
Basic form	[captures](params) { body }	Basic syntax, generates a closure type
No-parameter lambda	[captures] { body }	Shorthand that omits the parameter list
Capture by value	[x, y]	Captures variables by copying their values
Capture by reference	[&x, &y]	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	[captures](params) mutable { body }	Allows modifying the copies captured by value
Generic lambda	[captures](auto a, auto b) { body }	Parameters use auto, templated operator()
Explicit template parameters	[captures]<typename T>(T a) { body }	C++20, explicitly specifies a template parameter list
Static lambda	[captures](params) static { body }	C++23, operator() is a static member function

Minimal Example

#include <algorithm>
#include <vector>
#include <iostream>
// Standard: C++11
int main() {
    std::vector<int> v = {3, 1, 4, 1, 5};
    int threshold = 3;
    auto count = std::count_if(v.begin(), v.end(),
        [threshold](int x) { return x > threshold; });
    std::cout << count << "\n"; // Output: 2
}

Embedded Suitability: High

• The closure type is generated at compile time, with no heap allocation overhead and zero additional runtime cost
• Replaces function pointers and hand-written functors, making callback code more compact and more readable
• Watch out for the lifetime risks of reference captures in asynchronous or interrupt contexts; value capture is recommended for embedded callbacks
• C++14 generic lambdas let us 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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