CODEWITHSUNDEEP
c++c++11multidimensional-arraystl
TeaOverflow
TeaOverflow

Reputation: 2578

How does subscripting std::array multiple times work?

How does subscripting multiple times work for std::array even though all operator[]returns is a reference, without using any proxy-objects (as shown here)?

Example:

#include <iostream>
#include <array>

using namespace std;

int main()
{

    array<array<int, 3>, 4> structure;
    structure[2][2] = 2;
    cout << structure[2][2] << endl;

    return 0;
}

How/why does this work?

Upvotes: 2

Views: 100

Answers (2)

Baum mit Augen
Baum mit Augen

Reputation: 50063

You simply call structure.operator[](2).operator[](2), where the first operator[] returns a reference to the third array in structure to which the second operator[] is applied.

Note that a reference to an object can be used exactly like the object itself.

Upvotes: 7

Mike Seymour
Mike Seymour

Reputation: 254471

As you say, structure[2] gives a reference to an element of the outer array. Being a reference, it can be treated exactly as if it were an object of the same type.

That element is itself an array (array<int,3>), to which a further [] can be applied. That gives a reference to an element of the inner array, of type int.

Upvotes: 6

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