What is the meaning of square brackets before unary predictate

Asked Oct 25 '17 at 15:18

Active Oct 25 '17 at 16:34

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I was reading this code on Rosettacode: http://rosettacode.org/wiki/Closest-pair_problem#C.2B.2B

And I stumbled upon this strange function inside of std::copy_if()

std::copy_if(std::begin(yP), std::end(yP), std::back_inserter(yS),
[&minPair, &xM](const point_t& p) {
    return std::abs(xM - p.first) < minPair.first;
});

What does [&minPair, &xM] before function means?

Why function has no name and no return type? Compiler implicitly guesses that its bool?

edited Oct 25 '17 at 16:34

Thomas Matthews

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asked Oct 25 '17 at 15:18

ScienceDiscoverer

The would be the [capture](http://en.cppreference.com/w/cpp/language/lambda#Lambda_capture) of a [lambda expression](http://en.cppreference.com/w/cpp/language/lambda) – Cory Kramer Oct 25 '17 at 15:19
Thanks, didn't knew about lambdas. – ScienceDiscoverer Oct 25 '17 at 15:58

What is the meaning of square brackets before unary predictate

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