array<int> a, b;
a.At(1000) = 1;
b = a;
a[10] = 2;  <==ERROR
b[10] = 2;  <==OK

array<int> a, b;
a.At(1000) = 1;
b = a;      <== b and a share same memory area
a[10] = 2;  <== here an automatic deep copy, ok
b[10] = 2;  <== here no deep copy, just array access, ok

array<int> a, b;
a.At(1000) = 1;
b = a;      <== deep copy
a[10] = 2;  <==OK
b[10] = 2;  <==OK

array<int> a;
a = MyFunc(x);