[ruby-core:106553] [Ruby master Feature#18395] Introduce Array#subtract! for performance

Issue #18395 has been updated by byroot (Jean Boussier).


Have you benched `array.reject! { |e| array_or_set.include?(e) }`?

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Feature #18395: Introduce Array#subtract! for performance 
https://bugs.ruby-lang.org/issues/18395#change-95217

* Author: schneems (Richard Schneeman)
* Status: Open
* Priority: Normal
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PR: https://github.com/ruby/ruby/pull/5110#issuecomment-984345309

It is common to use `-=` to modify an array to remove elements. Also, there is `Array#difference` which accepts multiple arguments. Both of these methods allocate an intermediate array when the original array could be re-used.

I am proposing we add an API onto Array that allows the programmer to perform a subtraction/difference operation and mutate the original array.

I am proposing `Array#subtract!`. Reasons why I did not choose `Array#difference!` are discussed in the comments of the PR. I'm also happy to discuss alternative names.

```
ary = [0, 1, 1, 2, 1, 1, 3, 1, 1]
ary.subtract!([1]) #=> [0, 2, 3]
ary                #=> [0, 2, 3]

ary = [0, 1, 2, 3]
ary.subtract!([3, 0], [1, 3]) #=> [2]
ary                           #=> [2]
```



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