No trees in the stdlib?

[Hallvard B Furuseth]

Stefan Behnel writes:
>João Valverde wrote:
>> Besides some interface glitches, like returning None
>> on delete if I recall correctly.
>
> That's actually not /that/ uncommon. Operations that change an object are
> not (side-effect free) functions, so it's just purity if they do not have a
> return value.

It's purity that they don't return the modified tree/dict/whatever.
They can still return the deleted element and remain pure.

-- 
Hallvard