Advanced C++ multiple parentheses

Question

I'm reviewing a sample program code and found this line:

auto prerequisite = task<void>([](){});

What is the meaning of those combined parentheses ([](){})

I'm a cpp programmer but do not know advance cpp (c11+) which this Microsoft example is written at. Googling didn't help, and I don't know the name of those operators.

related/dup: https://stackoverflow.com/questions/7627098/what-is-a-lambda-expression-in-c11 — YSC, Jan 31 '19 at 10:44
I do not think it is a duplicate of https://stackoverflow.com/questions/7627098/what-is-a-lambda-expression-in-c11 . These are completely different questions. — Maxim Egorushkin, Jan 31 '19 at 14:38

Maxim Egorushkin · Accepted Answer · 2019-01-31T10:45:33.877

13

[](){} is a lambda expression that creates a function object that has non-zero size and does nothing.

This is probably to avoid checking whether prerequisite is valid/exists - it is always valid, but may do nothing.

edited Jan 31 '19 at 10:45

answered Jan 31 '19 at 10:40

Maxim Egorushkin

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Advanced C++ multiple parentheses

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