better pointer comparison

[moodymudskipper]

Just saw that we can get info on pointers with .Internal(inspect(x)).

Pointers can be different though even if they share the same adress, it's a bit like 2 environment sharing the same data and same parent, they're still different,they can have different metadata (protected, tag, attributes) . Our method of building a pointer from an adress actually builds a new pointer in this sense and it would be great if we could adapt it.

We can use this .Internal(inspect(x)) trick for other things like negative 0s etc

[moodymudskipper]

chatgpt gave me this to return a pointer from the R object's adress rather than just the adress.:

SEXP deref_sexp(SEXP address_str) {
  const char* cstr = CHAR(STRING_ELT(address_str, 0));
  uintptr_t addr = strtoull(cstr, NULL, 16);
  SEXP obj = (SEXP)(uintptr_t)addr;
  return obj;
}

so .xptr could use this adress instead. However it's less transparent because the user sees the target adress when printing the object.

We could also argue that it's good to create a copy rather than using the reference object.

So we could use the same strategy as .env() and provide extra info, an argument that's not used.

.xptr(object = "30412f5d0", target = "0x1290462e0")

Or maybe not to break code we keep the default that we have, and optionally we use (note the reversal and unnamed target) :

.xptr("0x1290462e0", object = "30412f5d0")

In the latter case the first arg is ignored, just displayed for info.