why () is () and [] is [] work in other way?

[Devin Jeanpierre]

On Sun, Apr 22, 2012 at 9:22 PM, Terry Reedy <tjreedy at udel.edu> wrote:
> On 4/22/2012 3:43 PM, John Nagle wrote:
>>
>> On 4/20/2012 9:34 PM, john.tantalo at gmail.com wrote:
>>>
>>> On Friday, April 20, 2012 12:34:46 PM UTC-7, Rotwang wrote:
>>>
>>>> I believe it says somewhere in the Python docs that it's undefined and
>>>> implementation-dependent whether two identical expressions have the same
>>>> identity when the result of each is immutable
>>
>>
>> Bad design. Where "is" is ill-defined, it should raise ValueError.
>
>
> There is no ambiguity about the meaning of 'is' in Python. It is always
> well-defined. So the suggestion is a nullity. The equivalent function form
> in Python is

Bollocks it's well defined. We've already agreed that "1 is 1" may or
may not return True. Then let's just go to the definition:
http://mathworld.wolfram.com/Well-Defined.html

"An expression is called "well-defined" (or unambiguous) if its
definition assigns it a unique interpretation or value. Otherwise, the
expression is said to not be well-defined or to be ambiguous. "

The same complaint applies to your suggestion that id() is
well-defined, and I stopped reading there.

-- Devin