[Python-Dev] Explicit Lexical Scoping (pre-PEP?)

[Jeremy Hylton]

On 7/12/06, Fredrik Lundh <fredrik at pythonware.com> wrote:
> Boris Borcic wrote:
>
> >> note that most examples of this type already work, if the target type is
> >> mutable, and implement the right operations:
> >>
> >>       def counter(num):
> >>           num = mutable_int(num)
> >>           def inc():
> >>               num += 1
> >>               return num
> >>           return inc
> >
> > I agree with you (and argued it in "scopes vs augmented assignment vs sets"
> > recently) that mutating would be sufficient /if/ the compiler would view
> > augmented assignment as mutations operators
>
> feel free to replace that += with an .add(1) method call; the point
> wasn't the behaviour of augmented assigment, the point was that that the
> most common use pattern involves *mutation* of the target object.
>
> the syntax isn't that important, really.

Mutation is different from rebinding.  A tuple is immutable, but you
can rebind the variable that refers to the tuple.  I think we will
confuse users if we use the term mutation to refer to name binding.
Name binding is already a subtle issue, so I think the risk is
significant.

Jeremy