From: merch-redmine@...
Date: 2021-03-05T22:37:36+00:00
Subject: [ruby-core:102750] [Ruby master Feature#17347] Enumerator::Chain of Enumerator::Lazy should be lazy

Issue #17347 has been updated by jeremyevans0 (Jeremy Evans).


This isn't a duplicate of #17216 even though it is related.  I agree that this feature would be useful.  I've included an implementation in the same pull request: https://github.com/ruby/ruby/pull/3811 

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Feature #17347: Enumerator::Chain of Enumerator::Lazy should be lazy
https://bugs.ruby-lang.org/issues/17347#change-90762

* Author: asilano (Chris Howlett)
* Status: Open
* Priority: Normal
----------------------------------------
ruby 2.6.6p146 (2020-03-31 revision 67876) [x86_64-linux]

Consider the following script:
``` ruby
a = [1,2,3].lazy
p a
b = [4,5,6].lazy
p b
c = a + b
p c
```

This gives the output:
```
#<Enumerator::Lazy: [1, 2, 3]>
#<Enumerator::Lazy: [4, 5, 6]>
#<Enumerator::Chain: [#<Enumerator::Lazy: [1, 2, 3]>, #<Enumerator::Lazy: [4, 5, 6]>]>
```

Note that `c` is just `Enumerator::Chain`; but all its component enumerators are lazy, so it would be nice if `c` were lazy.

That is, I'd like the output to be:
```
#<Enumerator::Lazy: [1, 2, 3]>
#<Enumerator::Lazy: [4, 5, 6]>
#<Enumerator::Lazy: #<Enumerator::Chain: [#<Enumerator::Lazy: [1, 2, 3]>, #<Enumerator::Lazy: [4, 5, 6]>]>>
```




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