[Python-Dev] PEP 246, redux

[Alex Martelli]

On 2005 Jan 11, at 18:27, Michael Chermside wrote:
    ...
> ... but in my world, people violate Liskov all the time, even
> in languages that attempt (unsuccessfully) to enforce it. [1]
    ...
> [1] - Except for Eiffel. Eiffel seems to do a pretty good job
>    of enforcing it.

...has Eiffel stopped its heroic efforts to support covariance...?  
It's been years since I last looked seriously into Eiffel (it was one 
of the languages we considered as a successor to Fortran and C as main 
application language, at my previous employer), but at that time that 
was one of the main differences between Eiffel (then commercial-only) 
and its imitator (freeware) Sather: Sather succumbed to mathematical 
type-theory and enforced contravariance, Effel still tried to pander 
for how the human mind works by allowing covariance (which implies a 
Liskov violation and is probably the main serious reason for it) and 
striving horrendously to shoehorn it in.  So what's the score now...?


Alex