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

[Nick Coghlan]

On 31 May 2016 3:12 pm, "Glenn Linderman" <v+python at g.nevcal.com> wrote:
>
> On 5/31/2016 12:55 PM, rndblnch wrote:
>>
>> Guido van Rossum <gvanrossum <at> gmail.com> writes:
>>
>>>
>>> Also -- the most important thing.  What to call these things? We're
>>> pretty much settled on the semantics and how to create them (A =
>>> NewType('A', int)) but what should we call types like A when we're
>>> talking about them? "New types" sounds awkward.
>>
>> back in high school, i was introduced to c programming with the
"disciplined
>> C" preprocessor [0].
>> it made the distinction between information type and representation type
>> (e.g. between the semantic and the implementation).
>> those new types where created using typedefs and were named 'parallel
types'
>> below is the relevant part of the dcc presentation:
>
>
> Interesting! Prior art. And parallel type isn't a bad name...

If I heard "parallel type", I'd assume it had something to do with parallel
processing.

Of the options suggested so far, DistinctType seems the most promising to
me.

Cheers,
Nick.

>
>>
>>
>> """
>> a major innovation of Disciplined C is the notion of "parallel type",
that
>> allows a distinction between information type and representation type.
The
>> following:
>>
>> typedef int Tindex, Tval;
>> typedef Tindex Trow, Tcol;
>>
>> creates four distinct types, but which all accept the same operations and
>> the same constants as the "representation" type ('int' here). Tindex,
Tval,
>> Trow and Tcol are examples of "information" types, because they convey an
>> idea of the semantics of the corresponding objects. For example, they
may be
>> put to use in a checkers playing program: Tval will name 'int's that
>> represent values of checkers, Trow and Tcol, 'int's that represent row
and
>> column indexes, Tindex, generic type for indexes.
>> Tindex, Tval, Trow and Tcol are called parallel types; in fact, a type
T1 is
>> said to be parallel to a type T2 iff both are defined through a chain of
>> typedefs starting from the same 'baseType', with no intervening qualifier
>> nor modifier (pointer/array/function decla- rator, see grammar in
Appendix
>> A). In other words, T and T2 must be strict synonyms of baseType.
>> """
>>
>> renaud
>>
>> 0. Disciplined C
>>
>> ACM SIGPLAN Notices Homepage archive
>> Volume 30 Issue 12, Dec. 1995
>> Pages 43 - 50
>> http://dl.acm.org/citation.cfm?id=219726.219747
>> http://www.digiater.nl/openvms/freeware/v50/dcc/dcc-v2_7d/dccarticle.ps
>>
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>
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