[ruby-core:111978] [Ruby master Feature#19324] Enumerator.product => Enumerable#product

Issue #19324 has been updated by duerst (Martin Dürst). Thinking about this a bit more, I guess both the "first argument is special" (A) and the "all arguments are the same" (B) have use cases. There's probably a third one, which is "all arguments are already in an array" (C). (B) and (C) are only one splat/[] away from each other; (A) is clearly a bit farther off from the other two, see `array_of_arrays.first.product(*array_of_arrays.drop(1))` above. Making a distinction by using the difference between method with receiver and class method is one way to accommodate these use cases, but I think it would be more Ruby-like if receivers where used in both cases and the distinction were made by method name. So as an example, we could have: `a.zip(b, c)` and `[a,b,c].multi_zip`. `multi_zip` here is only one possible name, there may be better ones. This solution would allow method chaining, which is important for good Ruby style. ---------------------------------------- Feature #19324: Enumerator.product => Enumerable#product https://bugs.ruby-lang.org/issues/19324#change-101415 * Author: zverok (Victor Shepelev) * Status: Open * Priority: Normal ---------------------------------------- I know it might be too late after introducing a feature and releasing a version, but I find `Enumerator.product` quite confusing, and can't find any justification in #18685. **Problem 1: It is `Array#product` but `Enumerator.product`** ```ruby [1, 2].product([4, 5]) # => [[1, 4], [1, 5], [2, 4], [2, 5]] # Usually, when we add methods to Enumerable/Enumerator which # already array had before, it is symmetric, say... [1, nil, 2, 3].compact #=> [1, 2, 3] [1, nil, 2, 3].lazy.compact.first(2) #=> [1, 2] # But not in this case: [1, 2].lazy.product([4, 5]).first(2) # undefined method `product' for #<Enumerator::Lazy: [1, 2]> (NoMethodError) # Because you "just" need to change it to: Enumerator.product([1, 2].lazy, [4, 5]).first(2) # => [[1, 4], [1, 5]] ``` No other method was "promoted" from Array this way And in general, I believe core methods tend to belong to the first object in the expression and not be free module methods, Elixir style. **Problem 2: It is one letter different from `Enumerator.produce`** I understand I might be biased here (as a person who proposed `produce`), and that method is not as popular (yet?) as I hoped, but still, two methods that do completely different things and differ by one letter, both being somewhat vague verbs (so it is easy to confuse them unless you did a lot of math and "product" is firmly set for set product in your head). I believe that EITHER of two problems would be concerning enough, but the combination of them seems to be a strong enough argument to make the change?.. (Maybe with graceful deprecation of module method in one next version, but, considering the Ruby 3.2 is just released, maybe vice versa, fix the problem in the next minor release?..) -- https://bugs.ruby-lang.org/