Quota from a good article from
http://www.cprogramming.com/c++11/c++11-lambda-closures.html
It turns out that the way lambdas are implemented is by creating a small class; this class overloads the operator(), so that it acts just like a function.
A lambda function is an instance of this class; when the class is constructed, any variables in the surrounding enviroment are passed into the constructor of the lambda function class and saved as member variables.
If you make a lambda with an empty capture group, [], rather than creating the class, C++ will create a regular function.
Here’s the full list of options:
| [] | Capture nothing (or, a scorched earth strategy?) |
| [&] | Capture any referenced variable by reference |
| [=] | Capture any referenced variable by making a copy |
| [=, &foo] | Capture any referenced variable by making a copy, but capture variable foo by reference |
| [bar] | Capture bar by making a copy; don’t copy anything else |
| [this] | Capture the this pointer of the enclosing class |
Dangers and Benefits of Capture by Reference
When you capture by reference, the lambda function is capable of modifying the local variable outside the lambda function–it is, after all, a reference. But this also means that if you return a lamba function from a function, you shouldn’t use capture-by-reference because the reference will not be valid after the function returns
According to bjarne stroustrup: Using lambdas can be convenient and terse, but also obscure. For nontrivial actions (say, more than a simple expression), I prefer to name the operation so as to more clearly state its purpose and to make it available for use in several places in a program.
References
http://www.cprogramming.com/c++11/c++11-lambda-closures.html
