What syntax is this: std::thread t([&] () { ... });?

Question

I was reading through the source code from Facebook's Proxygen, and I noticed some syntax I'd never seen before:

std::thread t([&] () {
    server.start();
});

Is it an anonymous method? And what is the value of &, is it the thread?

It looks confusing because if it is an anonymous method how is server accessible, isn't it out of scope?

It's a lambda. The `[&]` means that variables in the current scope are captured by reference (in this case `server`). — Daniel Kamil Kozar, Mar 20 '16 at 11:00
Its a *lambda function*. http://en.cppreference.com/w/cpp/language/lambda — Galik, Mar 20 '16 at 11:01

score 1 · Accepted Answer · answered Mar 20 '16 at 11:04

1

You are right, this code uses anonymous function. The basic syntax is : [capture-list] (list-params) { function-body}. So what [&] does is

captures all automatic variables odr-used in the body of the lambda by reference

You can read more here

answered Mar 20 '16 at 11:04

ig-melnyk

1 Answers1