Re: C++ vs D: Default param values and struct to array casting

[Johan Engelen via Digitalmars-d-learn]

On Friday, 6 September 2019 at 09:14:31 UTC, Andrew Edwards wrote:
C++ allows the for following:
struct Demo
{
        float a, b, c, d;
        Demo() { a = b = c = d = 0.0f; }
        Demo(float _a, float _b, float _c, float _d) {
                a = _a;
                b = _b;
                c = _c;
                d = _d;
        }
        float  operator[] (size_t i) const { return (&a)[i]; } //[3]

"(&a)[i]" is undefined behavior in C++. You cannot index into 
struct members like that. Of course it may work in certain cases, 
but UB is UB. Don't do it!

I found a more detailed explanation for you: 
https://stackoverflow.com/questions/40590216/is-it-legal-to-index-into-a-struct

-Johan