Re: Stack Overflow moderator “animuson”

Joshua Landau joshua at landau.ws
Wed Jul 10 19:55:29 CEST 2013


On 10 July 2013 17:18, Ethan Furman <ethan at stoneleaf.us> wrote:
> On 07/10/2013 08:54 AM, Joshua Landau wrote:
>>
>> On 10 July 2013 10:00, Steven D'Aprano <steve at pearwood.info> wrote:
>>>
>>> On Wed, 10 Jul 2013 07:55:05 +0000, Mats Peterson wrote:
>>>
>>>> A moderator who calls himself “animuson” on Stack Overflow doesn’t want
>>>> to face the truth. He has deleted all my postings regarding Python
>>>> regular expression matching being extremely slow compared to Perl.
>>>
>>>
>>> That's by design. We don't want to make the same mistake as Perl, where
>>> every problem is solved by a regular expression:
>>>
>>>
>>> http://neilk.net/blog/2000/06/01/abigails-regex-to-test-for-prime-numbers/
>>>
>>> so we deliberately make regexes as slow as possible so that programmers
>>> will look for a better way to solve their problem. If you check the
>>> source code for the re engine, you'll find that for certain regexes, it
>>> busy-waits for anything up to 30 seconds at a time, deliberately wasting
>>> cycles.
>>
>>
>> I hate to sound like this but do you realise that this is exactly what
>> you're arguing for when saying that sum() shouldn't use "+="?
>
>
> my_obj = SomeKoolClass()
> my_obj.modify_in_some_kool_way()
> new_result = sum([SKC1, SKC2, SKC3], my_obj)
>
> Guess what?  You've just changed my_obj.

You're extrapolating too quickly. The first "+" is a copying "+", the
rest add in-place to the new object. Thus, no unexpected side effect.



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