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

[Albert van der Horst]

In article <7xvckq4c2j.fsf at ruckus.brouhaha.com>,
Paul Rubin  <no.email at nospam.invalid> wrote:
>Kiuhnm <kiuhnm03.4t.yahoo.it> writes:
>> I can't think of a single case where 'is' is ill-defined.
>
>If I can't predict the output of
>
>    print (20+30 is 30+20)  # check whether addition is commutative
>    print (20*30 is 30*20)  # check whether multiplication is commutative
>
>by just reading the language definition and the code, I'd have to say
>"is" is ill-defined.

The output depends whether the compiler is clever enough to realise
that the outcome of the expressions is the same, such that only
one object needs to be created.

What is ill here is the users understanding of when it is appropriate
to use "is". Asking about identity of temporary objects fully
under control of the compiler is just sick.


Groetjes Albert

--
-- 
Albert van der Horst, UTRECHT,THE NETHERLANDS
Economic growth -- being exponential -- ultimately falters.
albert at spe&ar&c.xs4all.nl &=n http://home.hccnet.nl/a.w.m.van.der.horst