closure = decorator?

[Jussi Piitulainen]

Roy Smith writes:
> In article <m2a9ihxf3a.fsf at cochabamba.vanoostrum.org>,
>  Piet van Oostrum wrote:
> 
> > I usually say that a closure is a package, containing a function
> > with some additional data it needs. The data usually is in the
> > form of name bindings.
> 
> That's pretty close to the way I think about it.  The way it was
> originally described to me is, "A closure is a function bundled up
> with it's arguments".

Really? It should be more like "a function bundled up with some other
function's arguments" and even more like "a function bundled up with
bindings for its free variables".

And the data that makes a function a closure is bindings always, by
definition, not just usually.

> To make a real-life analogy, let's say you're modeling a parking
> garage.  I want to be able to walk up to the attendant and say,
> "Please bring my car around front at 5 O'Clock.  It's that one"
> (pointing to the slightly dented green Ford in spot 37).  So, you've
> got a class:
> 
> class DeliveryRequest:
>    def __init__(self, spot, time):
>       self.spot = spot
>       self.time = time
> 
> Now, over the course of the day, the garage attendants shuffle cars
> around to make room and retrieve vehicles that packed in the back.
> Comes 5 O'Clock, what vehicle do you want the attendant to deliver
> to the front?  The one that was in spot 37 at the time you made the
> request, or the one that's in spot 37 at 5 O'Clock?
> 
> Unless you want somebody else's car (perhaps you'd like something
> better than a slightly dented Ford), you want the attendant to
> capture the current state of spot 37 and remember that until 5
> O'Clock when it's time to go get the car, no matter where it happens
> to be right now.
> 
> That's a closure.

I fail to see a closure here. I see a class. I see an implied object
that could as well be dict(spot=37, time=5). Other entities (garage
and attendants) are not made sufficiently explicit.

There's another, more widely used word that means object. There's
another, more widely used word that means state. (I'm referring to the
words "object" and "state".) I see no need to use "closure" to mean
object or state, especially when the term has a more specific
established meaning.