[ruby-core:100174] [Ruby master Feature#17195] Freeze Enumerator::ArithmeticSequence objects

[ruby-core:100174] [Ruby master Feature#17195] Freeze Enumerator::ArithmeticSequence objects

[eregontp]

Issue #17195 has been reported by Eregon (Benoit Daloze).

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Feature #17195: Freeze Enumerator::ArithmeticSequence objects
https://bugs.ruby-lang.org/issues/17195

* Author: Eregon (Benoit Daloze)
* Status: Open
* Priority: Normal
----------------------------------------
Now, all Ranges are frozen (#15504).

Enumerator::ArithmeticSequence is very similar to Range, just with an extra `step`.
They're essentially already immutable, except that one could use set instance variables, but it seems of little use.

So, should we make Enumerator::ArithmeticSequence frozen too?



-- 
https://bugs.ruby-lang.org/

[ruby-core:100179] [Ruby master Feature#17195] Freeze Enumerator::ArithmeticSequence objects

[marcandre-ruby-core]

Issue #17195 has been updated by marcandre (Marc-Andre Lafortune).


Seems clear to me

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Feature #17195: Freeze Enumerator::ArithmeticSequence objects
https://bugs.ruby-lang.org/issues/17195#change-87752

* Author: Eregon (Benoit Daloze)
* Status: Open
* Priority: Normal
----------------------------------------
Now, all Ranges are frozen (#15504).

Enumerator::ArithmeticSequence is very similar to Range, just with an extra `step`.
They're essentially already immutable, except that one could use set instance variables, but it seems of little use.

So, should we make Enumerator::ArithmeticSequence frozen too?



-- 
https://bugs.ruby-lang.org/

[ruby-core:100187] [Ruby master Feature#17195] Freeze Enumerator::ArithmeticSequence objects

[eregontp]

Issue #17195 has been updated by Eregon (Benoit Daloze).


I just realized, this is problematic because `Enumerator::ArithmeticSequence` is a subclass of `Enumerator` and not of `Range`.
If it was a subclass of Range then I think it would be fine to freeze it.

But since it subclasses Enumerator, it has mutably methods like `Enumerator#next`:
```ruby
[7] pry(main)> enum = (1..5).step(2)
=> ((1..5).step(2))
[8] pry(main)> enum.next
=> 1
[9] pry(main)> enum.next
=> 3
[10] pry(main)> enum.next
=> 5
[11] pry(main)> enum.next
StopIteration: iteration reached an end
from (pry):11:in `next'
```

@mrkn do you remember why ArithmeticSequence is an Enumerator subclass and not a Range subclass?

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Feature #17195: Freeze Enumerator::ArithmeticSequence objects
https://bugs.ruby-lang.org/issues/17195#change-87758

* Author: Eregon (Benoit Daloze)
* Status: Open
* Priority: Normal
----------------------------------------
Now, all Ranges are frozen (#15504).

Enumerator::ArithmeticSequence is very similar to Range, just with an extra `step`.
They're essentially already immutable, except that one could use set instance variables, but it seems of little use.

So, should we make Enumerator::ArithmeticSequence frozen too?



-- 
https://bugs.ruby-lang.org/

[ruby-core:100346] [Ruby master Feature#17195] Freeze Enumerator::ArithmeticSequence objects

[muraken]

Issue #17195 has been updated by mrkn (Kenta Murata).


The reason why ArithmeticSequence is a subclass of Enumerator is for conserving the compatibility of the return types of `Range#step` and `Numeric#step`.

----------------------------------------
Feature #17195: Freeze Enumerator::ArithmeticSequence objects
https://bugs.ruby-lang.org/issues/17195#change-87958

* Author: Eregon (Benoit Daloze)
* Status: Open
* Priority: Normal
----------------------------------------
Now, all Ranges are frozen (#15504).

Enumerator::ArithmeticSequence is very similar to Range, just with an extra `step`.
They're essentially already immutable, except that one could use set instance variables, but it seems of little use.

So, should we make Enumerator::ArithmeticSequence frozen too?



-- 
https://bugs.ruby-lang.org/

[ruby-core:100350] [Ruby master Feature#17195] Freeze Enumerator::ArithmeticSequence objects

[eregontp]

Issue #17195 has been updated by Eregon (Benoit Daloze).

Status changed from Open to Rejected

Right, that makes sense, thanks for the reply.

Interestingly it seems `Enumerator#next` is still allowed even if the Enumerator is frozen, even though it is a kind of mutation.
I think that's a bug.

Given `ArithmeticSequence` has state through being an Enumerator, I think it's not reasonable to freeze, so I'll reject this issue.

----------------------------------------
Feature #17195: Freeze Enumerator::ArithmeticSequence objects
https://bugs.ruby-lang.org/issues/17195#change-87962

* Author: Eregon (Benoit Daloze)
* Status: Rejected
* Priority: Normal
----------------------------------------
Now, all Ranges are frozen (#15504).

Enumerator::ArithmeticSequence is very similar to Range, just with an extra `step`.
They're essentially already immutable, except that one could use set instance variables, but it seems of little use.

So, should we make Enumerator::ArithmeticSequence frozen too?



-- 
https://bugs.ruby-lang.org/