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

[Steven D'Aprano]

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