[Types-sig] File Protocol Proposal

[Paul Prescod]

Tim Hochberg wrote:
> 
> ...
>
> It's possible that this has changed, but according so section 2.1.1 of the
> Library Reference, everything is a boolean type! Or am I missing something.

That's true. It's also true that boolean functions in Python basically
always return 1 or 0 so there are really two different conventions at
work...
 
> The simple way is to just use union type. I called this composite in my
> orginal proposal, but that may be bad terminology. Anyway, the following
> should work:
> 
> def weeble(wobble : UnionOf(NoneType, String)):
>    # ....

Agreed. This is the right way.

> If we forced typecheck objects to all inherit from a common base class, it
> would also be pretty easy to write this as:
> 
> def weeble(wobble : NoneType | String):
>    # ....

Agreed on this too. But I was going to use the "or" keyword if at all
possible. I admit that the pipe symbol is more mathematically
conventional but "or" is more, er, English.

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