C++ iterate over vector of pairs with destructuring

Question

I've came across the following code:

vector<pair<int, int>> vec;
//...
for (auto &[f, s] : vec)
{
  //do something with f and s
}

how does this syntax work ([f, s] : vec) and since what standard was it introduced? Can I use it for getting field values from any struct/class or is it something specific to tuple/pairs?

Also, what is the performance impact of this approach?

In C++11 I was using auto in the following way:

for (auto &it : vec)
{
  //do something with it.first and it.second
}

Structure Binding: https://en.cppreference.com/w/cpp/language/structured_binding — Richard Critten, Jan 12 '20 at 15:14
Does this answer your question? [What are use cases for structured bindings?](https://stackoverflow.com/questions/45480824/what-are-use-cases-for-structured-bindings) — Yksisarvinen, Jan 12 '20 at 15:14

score 6 · Accepted Answer · answered Jan 12 '20 at 15:20

What you see here are structured bindings. For a full explanation of this feature see https://en.cppreference.com/w/cpp/language/structured_binding. Structured bindings were introduced in C++17. They provide a new syntax to give identifiers to members of a type.

In general, you can use structured bindings with your own types, too, but that requires a bit more effort. By default, arrays, tuple-like objects and aggregates are supported.

score 0 · Answer 2 · answered Jan 13 '20 at 12:09

0

Structured bindings is what you are looking for, otherwise you can make

template <typename T, typename N>
struct pair 
{ 
    T first; 
     N second; 
};

and iterate the C way, assuming your types can be copied, moved , assigned, etc.

answered Jan 13 '20 at 12:09

Ilian Zapryanov

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C++ iterate over vector of pairs with destructuring

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