C++20 STL Cookbook

Chapter 5: Lambda Expressions

The C++11 standard introduced the lambda expression (sometimes called the lambda function, or just lambda). This feature allows an anonymous function to be used in the context of an expression. Lambdas may be used in function calls, containers, variables, and other expression contexts. It may sound innocuous, but it's remarkably useful.

Let's start with a brief review of lambda expressions.

Lambda expressions

A lambda is essentially an anonymous function as a literal expression:

auto la = []{ return "Hello\n"; };

The variable la may now be used as if it were a function:

cout << la();

It can be passed to another function:

f(la);

It can be passed to another lambda:

const auto la = []{ return "Hello\n"; };

const auto ...