[Python-ideas] [Python-ideos] Dedicated overloadable boolean operators

[Guido van Rossum]

Well, there is still the issue of whether numpy would adopt PEP 335 even if
it was implemented. I'm still waiting for a response to my message
questioning how common `bool_value and/or numpy_array` really is.

Also, there may still be a significant difference between PEP 335 and your
proposal -- IIUC in your proposal if the value of the first operand
requires the second operand to be evaluated (e.g. `True or y`) then in your
proposal if y defined the 'r' special method it will be used; I don't think
PEP 335 does that. I like your version better.

On Mon, Nov 30, 2015 at 10:08 AM, Henry Schreiner <
henryschreineriii at gmail.com> wrote:

> I didn't realize the similarity of the proposals. I do think that testing
> for existence is better than running a method (that might not exist), at
> least from a high level perspective.
>
> So PEP 335 might be dusted off again and run through benchmarks? There
> seems to be at least a test implementation for Python 2.3, are there
> benchmarks documented somewhere? It sound like the version that adds new
> byte codes instead of an additional byte code per op was never included.
>
> I do like the cleanliness of not adding extra operators with nearly
> identical meanings.
>
> On Monday, November 30, 2015 at 11:24:12 AM UTC-6, Guido van Rossum wrote:
>>
>> On Mon, Nov 30, 2015 at 8:22 AM, Henry Schreiner <henrysch... at gmail.com>
>> wrote:
>>
>>> Sorry, the order was incorrect in that last message. It should be:
>>>
>>> When x and y is written, if x has __booland__, then x.__booland__(y) is
>>> returned. If not, then return x if x==False else if x==True, then if y
>>>  has y.__rbooland__(x), that is returned. If not, then return y
>>>
>>
>> This proposal isn't significantly different from PEP 335. In PEP 335,
>> first you ask the left operand whether to overload 'and' or not (by calling
>> its __and1__); if it says yes, you evaluate the second arg and ask the
>> first to evaluate it. In your proposal, the first question is answered by
>> inspecting whether x defines __booland__. I don't think this makes much
>> practical difference. The second part of your proposal is just a renaming
>> of __and2__/__rand2__ to __booland__/__rbooland__. I'm not sure I like this
>> much; the return type of these methods is almost never going to be an
>> actual bool, so the 'bool' in the name is somewhat misleading. (The names
>> chosen in PEP 335 are intentionally free of semantic hints, since the
>> intuition of someone who encounters these for the first time isn't likely
>> to be useful.)
>>
>> --
>> --Guido van Rossum (python.org/~guido)
>>
>


-- 
--Guido van Rossum (python.org/~guido)
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://mail.python.org/pipermail/python-ideas/attachments/20151130/0381c4ea/attachment-0001.html>