[ruby-core:97327] [Ruby master Feature#16665] Add an Array#except_index method

Issue #16665 has been updated by alex_golubenko (Alex Golubenko).


shevegen (Robert A. Heiler) wrote in #note-1:
> I can not comment on how useful this may be; I think I may have added something similar
> once in a while, but I can not say how useful or common that would be. IMO we should 
> see to determine how common the above idiom is, before we can say that it should be
> part of core ruby. (This is not necessarily a con-opinion from me, just that I think
> it may be better to assess how useful the addition would be, objectively).
> 
> There is one minor complaint that I have and I think it is about the name. The
> word "index" is used a lot so I guess we can expect a method that has "index" to
> do something with ... an index, or indici/indices - no problem there. But "except"
> is quite rare in ruby. Python has try/except clause. I believe that "except" as
> word is not completely fitting into ruby's parlance, as-is. I could be wrong :)
> but it does not "feel" very ruby-ish.
> 
> I can not offer a better alternative, but if we look at other ruby-method names,
> we have select, reject, filter ... and .each_with_index, and similar method 
> names. It may be best to be slowly considering whether "except" may be a good
> addition - not necessarily saying that it may be bad, but I am not sure it is
> a great name. (The name can be changed if the underlying suggestion has merit,
> so perhaps we should first evaluate whether the functionality is useful, 
> before finding an alternative name, or sticking to the suggested name.)

I also thought a lot about naming and have a few variants:
``` ruby
omit_indices

omit_index

values_out
```


----------------------------------------
Feature #16665: Add an Array#except_index method
https://bugs.ruby-lang.org/issues/16665#change-84449

* Author: alex_golubenko (Alex Golubenko)
* Status: Open
* Priority: Normal
----------------------------------------
The main idea is to implement a method that we can use to exclude elements from the array by their indices.

For example:

``` ruby
%w( a b c d e f).except_index(0, -1) 
=> ["b", "c", "d", "e"]

%w( a b c d e f g h ).except_index(0..1, 3, -2..-1)
=> ["c", "e", "f"]
```

I was meeting many questions on the StackOverflow about how to do such functionality also found many topics about it.
So I think it might a helpful addition.

I spent a few days finding the proper solution on Ruby that might be acceptable with integers and ranges(both positive and negative) and has good performance: 

```ruby
  def except_index(*indexes)
    indexes.each_with_object(dup) do |ind, obj|
      ind.is_a?(Range) ? ind.each { |i| obj[i] = false } : obj[ind] = false
    end.select(&:itself)
  end
```

As you can see it's have not the best readability so I think it's a good point to add a built-in method on C.



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