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Re: Immutability and Python

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2012/10/29 Chris Angelico <rosuav@gmail.com>:
> On Tue, Oct 30, 2012 at 2:55 AM, Paul Rubin <no.email@nospam.invalid> wrote:
>> andrea crotti <andrea.crotti.0@gmail.com> writes:
>>> and we want to change its state incrementing the number ...
>>>  the immutability purists would instead suggest to do this:
>>>     def increment(self):
>>>         return NumWrapper(self.number + 1)
>>
>> Immutability purists would say that numbers don't have "state" and if
>> you're trying to change a number's state by incrementing it, that's not
>> immutability.  You end up with a rather different programming style than
>> imperative programming, for example using tail recursion (maybe wrapped
>> in an itertools-like higher-order function) instead of indexed loops to
>> iterate over a structure.
>
> In that case, rename increment to next_integer and TYAOOYDAO. [1]
> You're not changing the state of this number, you're locating the
> number which has a particular relationship to this one (in the same
> way that GUI systems generally let you locate the next and previous
> siblings of any given object).
>
> ChrisA
> [1] "there you are, out of your difficulty at once" - cf WS Gilbert's "Iolanthe"
> --
> http://mail.python.org/mailman/listinfo/python-list


Yes the name should be changed, but the point is that they are both
ways to implement the same thing.

For example suppose I want to have 10 objects (for some silly reason)
that represent the next number, in the first case I would do:

numbers = [NumWrapper(orig.number)] * 10
for num in numbers:
    num.increment()

while in the second is as simple as:
numbers = [orig.next_number()] * 10

composing things become much easier, but as a downside it's not always
so easy and convienient to write code in this way, it probably depends
on the use case..

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Thread

Immutability and Python andrea crotti <andrea.crotti.0@gmail.com> - 2012-10-29 15:20 +0000
  Re: Immutability and Python Paul Rubin <no.email@nospam.invalid> - 2012-10-29 08:55 -0700
    Re: Immutability and Python Chris Angelico <rosuav@gmail.com> - 2012-10-30 03:08 +1100
    Re: Immutability and Python andrea crotti <andrea.crotti.0@gmail.com> - 2012-10-29 16:33 +0000
  Re: Immutability and Python Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2012-10-29 23:02 +0000
  Re: Immutability and Python rusi <rustompmody@gmail.com> - 2012-10-30 09:22 -0700
    Re: Immutability and Python Neal Becker <ndbecker2@gmail.com> - 2012-10-30 16:45 -0400
      Re: Immutability and Python rusi <rustompmody@gmail.com> - 2012-10-30 20:21 -0700
  Re: Immutability and Python Thomas Rachel <nutznetz-0c1b6768-bfa9-48d5-a470-7603bd3aa915@spamschutz.glglgl.de> - 2012-11-08 08:38 +0100

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