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I was checking an answer to a question posted on stackoverflow:

Answer to: C++, Sort One Vector Based On Another One

The answer has this piece of code:

std::sort(people.begin(), people.end(), 
               [](const auto& i, const auto& j) { return i.Score < j.Score; } );

I just want to understand why "[]" is put before the function here.

Thanks!

463035818_is_not_a_number
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Omar Waleed
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  • This is really a lambda, which is not exactly like a function. And `[]` Is used for captures; Lambdas can "capture" outside variables/references to outside variables and use them in the function definition. It's optional though, and in this case, the answerer chose to leave out captures because they weren't needed. – mediocrevegetable1 Feb 12 '21 at 13:06
  • `[](){}` part is basically an anonymous function. – Ayxan Haqverdili Feb 12 '21 at 13:10
  • imho it is amazing that `[](){}();` is now valid c++ syntax, especially if you consider how much code was necessary to achieve the same without a lambda expression – 463035818_is_not_a_number Feb 12 '21 at 13:13

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