[Python-Dev] Son of PEP 246, redux

[Michael Walter]

> instead interfaces can be defined in terms of individual operations, and 
> those operations can be initially defined by an abstract base, concrete 
> class, or an "interface" object.
I think this is quite problematic in the sense that it will force many
dummy interfaces to be created. At least without type inference, this
is a no-no.

Consider: In order to type a function like:

def f(x):
  # ...
  x.foo()
  # ...

...so that type violations can be detected before the real action
takes place, you would need to create a dummy interface as in:

interface XAsFUsesIt:
  def foo():
    pass

def f(x : XAsFUsesIt):
  # ...

...or you would want type inference (which at compile time types x as
"a thing which has a 'nullary' foo() function) and a type system like
System CT.

Former appears cumbersome (as it should really be done for every
function), latter too NIMPY-ish <wink>. What am I missing?

Sleepingly yours,
Michael


On Wed, 12 Jan 2005 23:48:47 -0500, Phillip J. Eby
<pje at telecommunity.com> wrote:
> At 11:26 PM 1/12/05 -0500, Clark C. Evans wrote:
> >Regardless,
> >getting back to the main goal I had when writing PEP 246 -- your
> >alternative proposal still doesn't seem to provide a mechanism for
> >component developers to have a dialogue with one another to connect
> >components without involving the application programmer.
> 
> Eh?  You still have adapt(); you still have adapters.  The only difference
> is that I've specified a way to not need "interfaces" - instead interfaces
> can be defined in terms of individual operations, and those operations can
> be initially defined by an abstract base, concrete class, or an "interface"
> object.  Oh, and you don't have to write adapter *classes* - you write
> adapting *methods* for individual operations.  This can be done by the
> original author of a class or by a third party -- just like with PEP 246.
> 
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