They're objects that mostly behave like arrays. You can't index element two of std::array foo as 1[foo] since it isn't an actual C array.

A Pascal array is just ones and zeros that behave like an array. So is a Fortran array.

> You can't index element two of std::array foo as 1[foo] since it isn't an actual C array.

That's just a silly quirk of C syntax that is deliberately not modeled in C++ operator overloading. It's not a real capability; it doesn't make arrays "do" anything new, so it' hard to call it an array behavior. It's a compiler behavior, that's for sure.

It could easily be added to C++, similarly to the way preincrement and postincrement are represented (which allows that obj++ and ++obj to be separate overloads).

   T &array_class::operator [] (int index) {
      // handles array[42]
   }

   T &array_class::operator [] (int index, int) {  // Fictional!!
      // handles 42[array]
   }

The dummy extra int parameter would mean "this overload of operator [] implements the flipped case, when the object is between the [ ] and the index is on the left".

C++ could easily have this; the technical barrier is almost nonexistent. (I wonder what the minimal diff against GNU C++ would be to get it going.)

I suspect that it's explicitly unwanted.

Ok, but who actually uses that?

The point is to demonstrate that std::array isn't an array.

What makes you so sure that if C got better arrays, those would be arrays, supporting a[i] i[a] commutativity and all?

That is predicated on equivalence to *(a + i) where a is a dumb pointer whose displacement commutes.

That is a quirk of C's arrays, no other language besides Assembly allows for that.

And even in Assembly, it depends on the CPU flavor which kind of memory accesses are available.

It depends entirely on the whims of the assembly language design. Assembly lanuages for the Motorola 68000 could allow operand syntax like like [A0 + offset], which could commute with [offset + A0], but the predominant syntax for that CPU family has it as offset(A0) which cannot be written A0(offset).

None of that changes what instruction is generated, just like C's quirk is one of pure syntax that doesn't affect the run-time.

Ok, fair. But for almost all practical purposes, std::array is an appropriate array replacement.