[Python-Dev] PEP 285: Adding a bool type

2002年3月30日 05:57:39 -0500

"Guido van Rossum" <guido@python.org> writ:
> Dear reviewers:
>> I'm particularly interested in hearing your opinion about the
> following three issues:
>> 1) Should this PEP be accepted at all.

Depends on the resolution of #2 and #3 ;-)
> 2) Should str(True) return "True" or "1": "1" might reduce
> backwards compatibility problems, but looks strange to me.
> (repr(True) would always return "True".)

str(True) must return 'True' or there isn't much point in bothering with
this, IMO.
> 3) Should the constants be called 'True' and 'False'
> (corresponding to None) or 'true' and 'false' (as in C++, Java
> and C99).

As a language interoperability guy, I prefer to keep as much precise
correspondence as possible with C++ (and Java), so I vote for
'true'/'false'.
> Most other details of the proposal are pretty much forced by the
> backwards compatibility requirement; e.g. True == 1 and
> True+1 == 2 must hold, else reams of existing code would break.

Guess what other language made that same choice for the same reasons?
> Minor additional issues:
>> 4) Should we strive to eliminate non-Boolean operations on bools
> in the future, through suitable warnings, so that e.g. True+1
> would eventually (e.g. in Python 3000 be illegal). Personally,
> I think we shouldn't; 28+isleap(y) seems totally reasonable to
> me.

Changing my position somewhat from earlier, I'll vote in my project's
self-interest: I agree with your inclination to allow bool to be
"promoted" to an int in these conditions.
> 5) Should operator.truth(x) return an int or a bool. Tim Peters
> believes it should return an int because it's been documented
> as such. I think it should return a bool; most other standard
> predicates (e.g. issubtype()) have also been documented as
> returning 0 or 1, and it's obvious that we want to change those
> to return a bool.

I agree again!
 6) Should we eventually remove the inheritance relationship
 between Int and Bool?
I hope so. Bool is-a Int doesn't seem like the right relationship to me,
unless perhaps we make Int is-a Long... naah, not even then.
-Dave