On Tue, Sep 26, 2017 11:00 PM, Steve D'Aprano <steve+pyt...@pearwood.info> wrote: > The critical distinction here is whether the names refer to each other: > >a <---> b > >or whether they merely refer to the same value: > >a ---> [ value ] <--- b > > >Python uses the second model. Var parameters in Pascal and references in C++ use >the first. Since the term "aliasing" is well-established for the first, using >it in Python *without making the difference clear* is wrong. > > >
Aha! There is the fundamental problem. In your first diagram below, if a is a pointer to b, and b is a pointer to a, then where is the value? If the value of 1 (or 2) is in a, then a cannot point at b; Or are you saying now that all variables in Pascal and C are _both_ values and pointers, simultaneously? Does that mean then that the value 1 (or 2) is in _both_ a and b? So that an assignment to either must change both copies of the value? No, I think it is more likely to be that the second diagram applies in all cases. Simply declaring a variable like A would lead to a --> [ uninitialized ] int& b creates an alias to a leads to a -> [ uninitialized ] <- b and then any assignment to a or b in the non-Python languages under consideration would fill in that box, allowing the change to be visible to both. But in Python, _all_ assignments are aliases. And I'll leave off further discussion by referring back to my previous note about what happens when we do "b = c" in the non-Python languages and in Python. >From the ordering of the notes in this forum, I will just assume you did not get a chance to read it before this post I am responding to. Roger Christman Pennsylvania State University -- https://mail.python.org/mailman/listinfo/python-list
