From: "eileencodes (Eileen Uchitelle) via ruby-core" <ruby-core@...>
Date: 2024-07-10T14:51:34+00:00
Subject: [ruby-core:118530] [Ruby master Bug#20623] Unexpected behavior of blocks in Enumerator::Lazy#zip

Issue #20623 has been updated by eileencodes (Eileen Uchitelle).


I tested this against a few versions of Ruby. In 2.7.x the first example returns `[1,2]`. But since 3.0.x it returns `1`. It also seems `cycle` isn't needed to reproduce it, so I removed that from the reproduction script. I wasn't able to get it any smaller, as `lazy` and `force` (or `to_a`) is required.

```
[1].lazy.zip([2].lazy).map do |x| 
  puts x.inspect
end.take(5).force

puts "---"

[1].lazy.zip([2].lazy).take(5).force.map do |x| 
  puts x.inspect
end
```

----------------------------------------
Bug #20623: Unexpected behavior of blocks in Enumerator::Lazy#zip
https://bugs.ruby-lang.org/issues/20623#change-109051

* Author: esad (Esad Hajdarevic)
* Status: Open
* ruby -v: 3.3.0
* Backport: 3.1: UNKNOWN, 3.2: UNKNOWN, 3.3: UNKNOWN
----------------------------------------
I've stumbled upon unexpected behaviour of lazy enumerators. My example:

```
[1].cycle.lazy.zip([2].cycle.lazy).map do |x|
  puts x.inspect
end.take(5).force
puts "---"
[1].cycle.lazy.zip([2].cycle.lazy).take(5).force.map do |x|
  puts x.inspect
end
```

The outputs (and variable assignment inside the block) differs


```
1
1
1
1
1
---
[1, 2]
[1, 2]
[1, 2]
[1, 2]
[1, 2]
```





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