Message349723
| Author |
gvanrossum |
| Recipients |
eryksun, gvanrossum, mark.dickinson, rhettinger, serhiy.storchaka, tim.peters, tomerv |
| Date |
2019年08月14日.17:42:21 |
| SpamBayes Score |
-1.0 |
| Marked as misclassified |
Yes |
| Message-id |
<1565804541.91.0.921807650744.issue37831@roundup.psfhosted.org> |
| In-reply-to |
| Content |
> > Because bool is embedded in int, it's okay to return a bool value *that compares equal to the int from the corresponding int operation*.
> Agreed that it's okay, but I'd like to understand why it's considered *desirable*. What use-cases benefit from having `x | y` give `True` or `False` rather than `1` or `0` when `x` and `y` are bools? Is the intent that `x & y` and `x | y` provide shorter ways to spell `x and y`, `x or y`, or (as I think Serhiy's suggesting) is this about catering to people coming from other languages and expecting `&` and `|` to be the right operations for doing logic with bools?
> From my integer-centric point of view, | and & are bitwise integer operations, not logical operations; they only *happen* to apply to bool because a bool is an int, but they're not natural boolean operations (in exactly the same way that +, -, *, etc. aren't natural boolean operations). "and" and "or" seem the "one obvious way to do it" for logical operations on bools; I don't think I understand why anyone would want to use | and & on bools to get another bool, instead of just using `or` and `and`.
For one thing, you can override `&` and `|` but you can't override `and` and `or`.
Probably when we introduced book we should have thought harder about it, but I don't think we should change anything at this point, so I'm not sure why whether it's worth trying to uncover the original deep motivations (probably they weren't so deep). |
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