[#122973] [PATCH] Add Gem.default_install — Felipe Contreras via ruby-core <ruby-core@...>
We need a way to enable user installs by default so that tools like
3 messages
2025/08/17
[ruby-core:123112] [Ruby Feature#20163] Introduce #bit_count method on Integer
From:
"tenderlovemaking (Aaron Patterson) via ruby-core" <ruby-core@...>
Date:
2025-08-28 19:42:09 UTC
List:
ruby-core #123112
Issue #20163 has been updated by tenderlovemaking (Aaron Patterson).
I would also like a `popcount` method. I prefer `popcount` over `bit_count`. I wrote my own [here](https://github.com/tenderlove/bitz/blob/93cedfe8f571e106ced753b3060c92507845e178/lib/bitz/set.rb#L332-L337) (but it only deals with single bytes).
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Feature #20163: Introduce #bit_count method on Integer
https://bugs.ruby-lang.org/issues/20163#change-114429
* Author: garrison (Garrison Jensen)
* Status: Open
----------------------------------------
This feature request is to implement a method called #bit_count on Integer that returns the number of ones in the binary representation of the absolute value of the integer.
```
n = 19
n.bit_count #=> 3
(-n).bit_count #=> 3
```
This is often useful when you use an integer as a bitmask and want to count how many bits are set.
This would be equivalent to
```
n.to_s(2).count("1")
```
However, this can be outperformed by
```
def bit_count(n)
count = 0
while n > 0
n &= n - 1 # Flip the least significant 1 bit to 0
count += 1
end
count
end
```
I think this would be a useful addition because it would fit alongside the other bit-related methods defined on integer: `#bit_length,` `#allbits?`, `#anybits?`, `#nobits?`. Also, when working with bitmasks, a minor upgrade to performance often results in a significant improvement.
Similar methods from other languages:
https://docs.python.org/3/library/stdtypes.html#int.bit_count
https://doc.rust-lang.org/std/primitive.i32.html#method.count_ones
--
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