[ruby-core:92605] [Ruby trunk Feature#11797] `Enumerator#with_object` with multiple objects

Issue #11797 has been updated by sawa (Tsuyoshi Sawada).


I now realize that, for the given use case, I can use `with_object` multiple times as follows:

```ruby
e
.each.with_object({}).with_object([]) {|(c, h), a| h[c] ? a.push(c) : h.store(c, true)}
.uniq
```

So I withdraw this feature request. Please close it.

----------------------------------------
Feature #11797: `Enumerator#with_object` with multiple objects
https://bugs.ruby-lang.org/issues/11797#change-77964

* Author: sawa (Tsuyoshi Sawada)
* Status: Open
* Priority: Normal
* Assignee: 
* Target version: 
----------------------------------------
Sometimes, when working with `Enumerator#with_object`, I want to keep some additional temporary objects besides the one to return. A use case is as follows (I got this from this StackOverflow question: http://stackoverflow.com/questions/3418123). Suppose I have an enumerator created from an array:

    e = ["a", "b", "c", "c", "a", "c"].to_enum

and want to get an array of its repeated elements in the order they are repeated (i.e., appears for the second time):

    # => ["c", "a"]

I can do it using `Enumerator#with_object` like this:

    e.to_enum.with_object([{}, []]){|c, (h, a)| h[c] ? a.push(c) : h.store(c, true)}.last.uniq

Here, I am getting the array referred to as `a` in the block, but besides that, I am using a temporal hash `h`. I thought it would be nice if `Enumerator#with_object` accepts one or more objects, pass them individually as block arguments, and returns only the last argument so that I can do this:

    e.to_enum.with_object({}, []){|c, h, a| h[c] ? a.push(c) : h.store(c, true)}.uniq




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