Verifiably better, validated Enum for Python

[Rustom Mody]

On Friday, May 26, 2017 at 5:31:54 PM UTC+5:30, Chris Angelico wrote:
> On Fri, May 26, 2017 at 9:46 PM, Steve D'Aprano wrote:
> >
> >> And yes, Steve, this is a challenge to you: if you think C's undefined
> >> behaviour is an abomination that should not be allowed to exist,
> >
> > CPython doesn't have to define the behaviour here. In *that* sense, the
> > ordinary, regular sense, it is undefined. The implication of that is that
> > whatever happens will happen according to some deterministic but
> > unpredictable (to you, the developer, at least) chain of cause and effect
> > that depends on the implementation. Probably something bad.
> >
> > That's fine. The Python language does not have to define the behaviour of
> > programs which abuse ctypes like that. If you do so, then whatever happens
> > will happen.
> >
> > That's not how the C standard defines "undefined behaviour", or the
> > implication of such.
> 
> Can you explain to me how it's different? Either way, the
> implementation is allowed to do what it likes, because you shouldn't
> be doing that.

I am guessing that Steven is mixing up undefined and unspecified behavior

Undefined : Implementation can do whatever it likes; erroring out or not
Unspecified : 
| use of an unspecified value, or other behavior where this International Standard
| provides two or more possibilities and imposes no further requirements on which 
| is chosen in any instance