Lambda Expressions and Closures

Lambdas (anonymous function objects) are a cornerstone of Functional Programming in C++. A lambda consists of a capture list, parameters, an optional return type, and a body.

The Capture List [ ]

• [] - Captures nothing.
• [=] - Captures all local variables by value.
• [&] - Captures all local variables by reference.
• [this] - Captures the current object by pointer.
• [*this] (C++17) - Captures the current object by value (safe for async).

Mutable Lambdas

By default, the operator() of a lambda is const (you cannot modify variables captured by value). Use mutable to allow modification.

int x = 10;
auto f = [x]() mutable { x++; return x; }; // OK

Generic Lambdas (C++14) and Templex Lambdas (C++20)

C++20 allows explicit template parameters in lambdas: []<typename T>(std::vector<T> const& v) { ... }.