[Python-ideas] IntFlags

[Neil Girdhar]

Even if you constrain yourself to the BitFlags rather than the more general
BitFields, I strongly disagree with the interface that people are proposing
involving & and ~ operators.  In general, good interface design reflects
the way we think about objects — not their underlying representation.  The
fact is that a BitSet's main operations are set and clear individual bits.
It is as if the BitFlags are a namedtuple with Boolean elements whose
underlying storage happens to be an integer.  Therefore, the interface that
makes the most sense is member access:

my_bit_flags.some_bit = True
my_bit_flags.some_bit = False

I don't see the justification for writing these as

my_bit_flags |= TheBitFlagsClass.some_bit
my_bit_flags &= ~TheBitFlagsClass.some_bit

The second line is particularly terrible because it exposes you to making
mistakes like:

my_bit_flags &= TheBitFlagsClass.some_bit
my_bit_flags |= ~TheBitFlagsClass.some_bit

— both of which are meaningless.

It also makes it hard to convert code between the alternate implementation
of using a namedtuple.  It should be easy to do that in my opinion.

Best,

Neil

On Thu, Mar 5, 2015 at 12:57 PM, Serhiy Storchaka <storchaka at gmail.com>
wrote:

> On 05.03.15 19:29, Neil Girdhar wrote:
>
>> Have you looked at my IntFields generalization of IntFlags?  It seems
>> that many of your examples (permissions, e.g.) are better expressed with
>> fields than with flags.
>>
>
> It looks too complicated for such simple case. And it has an interface
> incompatible with plain int.
>
>
>
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