C++ 17 in CoCalc

#include <iostream>
auto hello = "Hello World!";
std::cout << hello;

// or just
hello

auto num = 1+1;
num

struct MyObj {
  int value{ 123 };
  auto getValueCopy() {
    return [*this] { return value; };
  }
  auto getValueRef() {
    return [this] { return value; };
  }
};

MyObj mo;
auto valueCopy = mo.getValueCopy();
auto valueRef = mo.getValueRef();

mo.value = 321;
valueCopy(); // 123

valueRef(); // 321

std::array<int, 5> a{ 1, 2, 3, 4, 5 };
for (int& x : a)  {
    x = 2*x + 1;
}

#include <iostream>
for(auto const& x: a) {
  std::cout << x << " ";
}