[Python-Dev] Adding NewType() to PEP 484

[Ivan Levkivskyi]

My final vote goes to "distinct type alias".
But how should we call the function? NewType? Or should we change it to
DistinctAlias or something?

--
Ivan
28 Тра 2016 19:14 "Guido van Rossum" <guido at python.org> пише:

> Ohhhhh, another D-word! I really like distinct.
>
> On Sat, May 28, 2016 at 8:19 AM, Steve Dower <steve.dower at python.org>
> wrote:
> > Did anyone suggest "distinct type alias"?
> >
> > Regardless of what name, I'm fairly sure people will call it whatever the
> > function to create it is called. So if the function is
> > typings.distinguish_type(...), then distinguished will stick.
> >
> > Top-posted from my Windows Phone
> > ________________________________
> > From: Guido van Rossum
> > Sent: ‎5/‎28/‎2016 7:38
> > To: Steven D'Aprano
> > Cc: Python-Dev
> > Subject: Re: [Python-Dev] Adding NewType() to PEP 484
> >
> > Just to add to the list of options, Twitter also came up with
> >
> > - invention
> >
> > - DomainType
> >
> > - TypedAlias
> >
> > But seriously I think we should just decide between Derived Type and
> > Distinguished Type [Alias].
> >
> > The latter comes from the idea that when you write e.g.
> >
> > UserId = int
> >
> > then UserId is a type alias (that's existing PEP 484 terminology) and
> > the type checker doesn't distinguish it from int -- you can use it in
> > places where you logically expect a UserId but to the type checker
> > those variables have the type int.
> >
> > There is even a neat potential "origin story" that would explain why
> > we'd call it Distinguished Type Alias.
> >
> > The story is about gradually converting a large code base to being
> > consistent: initially you make UserId a regular type alias and you
> > start putting it in your code incrementally, making sure it has no
> > mypy errors as you go (but this just treats it as an int). After days,
> > when you think you are done, you change UserId to a distinguished type
> > alias and then mypy will point out the places where you've missed
> > something or you're doing something questionable with user IDs.
> >
> > And yes, in the wider context of subclassing, Derived Type is probably
> > confusing because a subclass is also called a derived class.
> >
> >
> > On Sat, May 28, 2016 at 5:24 AM, Steven D'Aprano <steve at pearwood.info>
> > wrote:
> >> On Fri, May 27, 2016 at 09:26:29PM -0700, Guido van Rossum wrote:
> >>
> >>> We discussed this over dinner at PyCon, some ideas we came up with:
> >>>
> >>> - Dependent types, harking back to a similar concept in Ada
> >>> (
> https://en.wikibooks.org/wiki/Ada_Programming/Type_System#Derived_types)
> >>> which in that language is also spelled with "new".
> >>
> >> I started to explain this to my non-programmer wife, I got as far as
> >> explaining types, and that we need a name for this thing, and she
> >> stopped me and said
> >>
> >> "Please don't tell me this is leading to TypyMcTypeCheck."
> >>
> >> [...]
> >>> - BoatyMcBoatType
> >>
> >>> The nice thing about "distinguished" is that it's a relatively rare
> >>> word so it is easy to remember or look up.
> >>
> >> I would have thought that being rare, it would be *harder* to remember.
> >>
> >>
> >>> Personally I'm still in favor of Derived type (but I'm more into
> >>> ancient programming languages than most folks here). I could also live
> >>> with Distinguished Type.
> >>
> >> I think Derived Type is the nicest of the options. It accurately
> >> describes what it is: a type derived from another. And its shorter and
> >> easy to both say and write than "Distinguished type" (which sounds like
> >> "distinguished gentlemen" -- is it wearing a monocle and a top hat?).
> >>
> >> "Distinguished" is too vague for my tastes, it might as well be
> >> "flibblegubble type". *All* types are distinguished, the type checker
> >> has to distinguish int from float from list from str, so to call
> >> NewType("userid", int) a "distinguished type" is only to call it a type.
> >>
> >>
> >>
> >> --
> >> Steve
> >> _______________________________________________
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> >> Python-Dev at python.org
> >> https://mail.python.org/mailman/listinfo/python-dev
> >> Unsubscribe:
> >> https://mail.python.org/mailman/options/python-dev/guido%40python.org
> >
> >
> >
> > --
> > --Guido van Rossum (python.org/~guido)
> > _______________________________________________
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> >
> https://mail.python.org/mailman/options/python-dev/steve.dower%40python.org
>
>
>
> --
> --Guido van Rossum (python.org/~guido)
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