Lambda Expressions (C++11)

In a Nutshell

Lambda expressions allow us to define an anonymous function object inline, commonly used to pass short logic as an argument to algorithms or callbacks.

Header

None (language feature)

Core API Quick Reference

Operation	Signature	Description
Non-capturing lambda	[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
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 }	Uses auto for parameters, 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"; // 输出: 2
}

Embedded Applicability: High

• Closure types are generated at compile time with no heap allocation overhead and zero extra runtime cost
• Replaces function pointers and hand-written functors, making callback code more compact and readable
• Beware of lifetime risks with reference captures in asynchronous or interrupt scenarios; value capture is recommended for embedded callbacks
• C++14 generic lambdas allow us to write generic sorting or search 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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