Why is non-const std::array::operator[] not constexpr?

Question

I\'m trying to fill a 2D array on compile time with a given function. Here is my code:

template
struct Table
{
  int data[H][W];
  //std:         


        

Answer 1

While my first thought was "why would you need a constexpr method on a non-const array"? ...

I then sat down and wrote a little test to see if the idea made sense:

#include 

using namespace std;
struct X{

    constexpr X()
    : _p { 0, 1, 2, 3, 4, 5, 6, 7, 9 }
    {
    }

    constexpr int& operator[](size_t i)
    {
        return _p[i];
    }

    int _p[10];
};

constexpr int foo()
{
    X x;
    x[3] = 4;
    return x[3];
}


auto main() -> int
{
    cout << foo() << endl;

    return 0;
}

It turns out that it does.

So I'm drawing the conclusion that the committee took the same "obvious" view that I did and discounted the idea.

Looks to me as if a proposal could be put forward to the committee to change it in c++17 - giving this question as an example.