[Python-ideas] Python Numbers as Human Concept Decimal System

[Chris Angelico]

On Fri, Mar 7, 2014 at 9:23 AM, Mark H. Harris <harrismh777 at gmail.com> wrote:
>        Well, there it is.   The idea is that any function or method that
> takes a  Number reference
> or a  PythonNumber  reference does not have to interrogate what type of
> Number it is... it just
> works (why?) glad you asked, because of polymorphism and a three pointer hop
> down a virtual
> function table!

That's way too concrete for Pythonic style :)

All you need to do is have each numeric type implement the same
operations, and there you are, as the Lord Chancellor said, out of
your difficulty at once!

And that's what we already have. You can add two numbers and they'll
simply add. In fact, a C++ style "hop down a virtual function table"
couldn't handle that. I could make a class hierarchy like you
describe, and have each one have an add() method or operator+(), but
somewhere along the line, something still has to cope with the fact
that it could be given any sort of number - there has to be code
someplace that handles the adding of a (Decimal) Real and a Real_b,
because some day, someone's going to do it. (The correct response
might be to raise TypeError, on the basis that that action merges two
separate inaccuracies. But more likely, the correct response is to
convert one of them to the other type.)

What does your proposed hierarchy offer that numbers.Number doesn't?

ChrisA