[Types-sig] Interface PEP

[Paul Prescod]

Michel Pelletier wrote:
> 
>...
> 
> Well, the syntax is a secondary issue, I'm concerned more with the model.
> I think what you are saying is that my proposal specifies that
> specification and implementation must be seperate.  Or maybe you are
> saying what you said, in that case, you lost me.

I think I was saying what I said. :)

Your syntax:

interface ReadableFile:
    def read(size):
        pass

>>> print dir(ReadableFile)
[...., implementedBy, ...]

>>> class MyReadFile implements ReadFile:
...     ...


My syntax:

>>> class _ReadableFile:
...     def __implementedby___(self, obj):
...         return hasattr(obj, read)
... ReadFile = _ReadableFile()

>>> class MyReadFile:
...      __implements__=[ReadFile]


> > Mine are basically functional interfaces (in fact
> > they could really be functions instead of classes).
> 
> You lost me there too. ;)

The operative part of my interfaces is the __implementedby__ method.
What you say in a bunch of method declarations, I say in
__implementedby__

> > Your interface objects have an implicitly generated implementedBy
> > method. Mine have an explicit method.
> 
> I don't get this either, can you be more explicit about your explicitness,
> also by "your" I assume you mean me?  Above you were referring to me in
> the third person, so I'm lost yet again.

You create objects that don't LOOK like they have an implementedBy
method, but they really do (implicit). I require the creation of an
explicit __implementedby__ method.

The interface syntax version is more compact and readable for
complicated interfaces. The functional version is more flexible. They
will probably work together well as alternate syntaxes.

-- 
Python:
    Programming the way
    Guido
    indented it.
       - (originated with Skip Montanaro?)