[ruby-core:95419] [Ruby master Feature#16261] Enumerable#each_tuple

[ruby-core:95419] [Ruby master Feature#16261] Enumerable#each_tuple

[zverok.offline]

Issue #16261 has been reported by zverok (Victor Shepelev).

----------------------------------------
Feature #16261: Enumerable#each_tuple
https://bugs.ruby-lang.org/issues/16261

* Author: zverok (Victor Shepelev)
* Status: Open
* Priority: Normal
* Assignee: 
* Target version: 
----------------------------------------
New method proposal.

Prototype code:
```ruby
module Enumerable
  def each_tuple
    return to_enum(__method__) unless block_given?
    each { |item| yield(*item) } # unpacking possible array into several args
  end
end
```

Supposed documentation/explanation:

> For enumerable with Array items, passes all items in the block provided as a separate arguments. t could be useful if the provided block has lambda semantics, e.g. doesn't unpack arguments automatically. For example:

  ```ruby
files = ["README.md", "LICENSE.txt", "Contributing.md"]
content = [fetch_readme, fetch_license, fetch_contributing] # somehow make a content for the files

files.zip(content).each_tuple(&File.:write) # writes to each file its content
```

> When no block passed, returns enumerator of the tuples:

  ```ruby
[1, 2, 3].zip([4, 5, 6]).each_tuple.map(&:+) # => [5, 7, 9] 
```



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

[ruby-core:95422] [Ruby master Feature#16261] Enumerable#each_tuple

[shevegen]

Issue #16261 has been updated by shevegen (Robert A. Heiler).


Hmmmm.

A slight issue I see with the name "tuple", and then the implicit name addition
".each_tuple", which would then (indirectly) elevate the term tuple.

I know the word tuple from e. g. using tuple in python, but I much prefer ruby's
way to name things (not only because I used ruby for a longer time than python,
but because I think the names in ruby make more sense in general e. g. Array/Hashes
versus List/Dictionaries).

I am not sure if we have "tuples" in ruby core/stdlib yet. I did however google
and find it in Rinda ... so at the least Rinda in stdlib has tuples. :P
https://ruby-doc.org/stdlib-2.6.5/libdoc/rinda/rdoc/Rinda/Tuple.html
(Not sure about ruby core, though.)

There is also a slight issue with intrinsic complexity (in my opinion), but this
is a lot due to one's personal style and preferences, so I will not comment 
much on that part - some ruby users prefer simplicity, others prefer more
flexibility in usage (aka more complex use cases). But I think the name itself
should be considered as well;  for the use of .each_tuple, ruby users would
first have to understand what a tuple is. Compare this to e. g. .each_pair
which is a LOT simpler to understand even to genuinely new people. I also
admit that this is not a very strong argument per se, since we have other
variants of .each* already, such as .each_with_index - but I still think
we should be careful which .each* variants are added. I also have no
alternative name proposal, my apologies.

----------------------------------------
Feature #16261: Enumerable#each_tuple
https://bugs.ruby-lang.org/issues/16261#change-82175

* Author: zverok (Victor Shepelev)
* Status: Open
* Priority: Normal
* Assignee: 
* Target version: 
----------------------------------------
New method proposal.

Prototype code:
```ruby
module Enumerable
  def each_tuple
    return to_enum(__method__) unless block_given?
    each { |item| yield(*item) } # unpacking possible array into several args
  end
end
```

Supposed documentation/explanation:

> For enumerable with Array items, passes all items in the block provided as a separate arguments. t could be useful if the provided block has lambda semantics, e.g. doesn't unpack arguments automatically. For example:

  ```ruby
files = ["README.md", "LICENSE.txt", "Contributing.md"]
content = [fetch_readme, fetch_license, fetch_contributing] # somehow make a content for the files

files.zip(content).each_tuple(&File.:write) # writes to each file its content
```

> When no block passed, returns enumerator of the tuples:

  ```ruby
[1, 2, 3].zip([4, 5, 6]).each_tuple.map(&:+) # => [5, 7, 9] 
```



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

[ruby-core:95424] [Ruby master Feature#16261] Enumerable#each_tuple

[shannonskipper]

Issue #16261 has been updated by shan (Shannon Skipper).


This reminds me of a neat post showing applicatives in pictures: http://adit.io/posts/2013-04-17-functors,_applicatives,_and_monads_in_pictures.html#applicatives

In Haskell:
```
[(*2), (+3)] <*> [1, 2, 3]
```

Or with this proposal in Ruby:
```
[2.:*, 3.:+].product([1, 2, 3]).each_tuple.map(&:call)
```

----------------------------------------
Feature #16261: Enumerable#each_tuple
https://bugs.ruby-lang.org/issues/16261#change-82178

* Author: zverok (Victor Shepelev)
* Status: Open
* Priority: Normal
* Assignee: 
* Target version: 
----------------------------------------
New method proposal.

Prototype code:
```ruby
module Enumerable
  def each_tuple
    return to_enum(__method__) unless block_given?
    each { |item| yield(*item) } # unpacking possible array into several args
  end
end
```

Supposed documentation/explanation:

> For enumerable with Array items, passes all items in the block provided as a separate arguments. t could be useful if the provided block has lambda semantics, e.g. doesn't unpack arguments automatically. For example:

  ```ruby
files = ["README.md", "LICENSE.txt", "Contributing.md"]
content = [fetch_readme, fetch_license, fetch_contributing] # somehow make a content for the files

files.zip(content).each_tuple(&File.:write) # writes to each file its content
```

> When no block passed, returns enumerator of the tuples:

  ```ruby
[1, 2, 3].zip([4, 5, 6]).each_tuple.map(&:+) # => [5, 7, 9] 
```



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

[ruby-core:95464] [Ruby master Feature#16261] Enumerable#each_tuple

[daniel]

Issue #16261 has been updated by Dan0042 (Daniel DeLorme).


It's worth pointing out the desired difference with regards to lambdas a bit more explicitly:

```ruby
[1, 2, 3].zip([4, 5, 6]).map(&:+)            # ArgumentError (wrong number of arguments (given 0, expected 1))
[1, 2, 3].zip([4, 5, 6]).each_tuple.map(&:+) # => [5, 7, 9]
```

But in that case it seems to me the behavior you want is the *opposite* of a tuple. Where a tuple is a struct-like set of n elements like `[1, 4]`, what you want here is to destructure that tuple in order to pass each element as an argument of a lambda. So it should be called maybe `each_splat` and the *inverse* operation would be called `each_tuple`.

Or how about something like this based on Enumerator? (hopefully without the hacks)

```ruby
class Enumerator
  def splat
    return to_enum(:splat) unless block_given?
    #each{ |item| yield(*item) } #this doesn't always work
    each{ |first,*rest| yield(first,*rest) } #hacky solution
  end
  def tuple
    return to_enum(:tuple) unless block_given?
    #each{ |*item| yield(item) } #this doesn't always work
    each{ |first,*rest| yield([first,*rest]) } #hacky solution
  end
end

pairs = [10, 20, 30].zip([10, 16, 20])
pairs.each.map(&:to_s)       #=> ["[10, 10]", "[20, 16]", "[30, 20]"]
pairs.each.tuple.map(&:to_s) #=> ["[10, 10]", "[20, 16]", "[30, 20]"]
pairs.each.splat.map(&:to_s) #=> ["10", "14", "1a"]

%i[a b c].each_with_index.map(&:inspect)       # ArgumentError (wrong number of arguments (given 1, expected 0))
%i[a b c].each_with_index.tuple.map(&:inspect) # => ["[:a, 0]", "[:b, 1]", "[:c, 2]"]
%i[a b c].each_with_index.splat.map(&:inspect) # ArgumentError (wrong number of arguments (given 1, expected 0))
```


----------------------------------------
Feature #16261: Enumerable#each_tuple
https://bugs.ruby-lang.org/issues/16261#change-82234

* Author: zverok (Victor Shepelev)
* Status: Open
* Priority: Normal
* Assignee: 
* Target version: 
----------------------------------------
New method proposal.

Prototype code:
```ruby
module Enumerable
  def each_tuple
    return to_enum(__method__) unless block_given?
    each { |item| yield(*item) } # unpacking possible array into several args
  end
end
```

Supposed documentation/explanation:

> For enumerable with Array items, passes all items in the block provided as a separate arguments. t could be useful if the provided block has lambda semantics, e.g. doesn't unpack arguments automatically. For example:

  ```ruby
files = ["README.md", "LICENSE.txt", "Contributing.md"]
content = [fetch_readme, fetch_license, fetch_contributing] # somehow make a content for the files

files.zip(content).each_tuple(&File.:write) # writes to each file its content
```

> When no block passed, returns enumerator of the tuples:

  ```ruby
[1, 2, 3].zip([4, 5, 6]).each_tuple.map(&:+) # => [5, 7, 9] 
```



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

[ruby-core:95465] [Ruby master Feature#16261] Enumerable#each_tuple

[zverok.offline]

Issue #16261 has been updated by zverok (Victor Shepelev).


@Dan0042 super-good points, thanks!

I'd say that `Enumerable#each_tuple`/`Enumerable#each_splat` + `Enumerator#tuple`/`Enumerator#splat` is a most powerful and straightforward combination.

----------------------------------------
Feature #16261: Enumerable#each_tuple
https://bugs.ruby-lang.org/issues/16261#change-82235

* Author: zverok (Victor Shepelev)
* Status: Open
* Priority: Normal
* Assignee: 
* Target version: 
----------------------------------------
New method proposal.

Prototype code:
```ruby
module Enumerable
  def each_tuple
    return to_enum(__method__) unless block_given?
    each { |item| yield(*item) } # unpacking possible array into several args
  end
end
```

Supposed documentation/explanation:

> For enumerable with Array items, passes all items in the block provided as a separate arguments. t could be useful if the provided block has lambda semantics, e.g. doesn't unpack arguments automatically. For example:

  ```ruby
files = ["README.md", "LICENSE.txt", "Contributing.md"]
content = [fetch_readme, fetch_license, fetch_contributing] # somehow make a content for the files

files.zip(content).each_tuple(&File.:write) # writes to each file its content
```

> When no block passed, returns enumerator of the tuples:

  ```ruby
[1, 2, 3].zip([4, 5, 6]).each_tuple.map(&:+) # => [5, 7, 9] 
```



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

[ruby-core:95473] [Ruby master Feature#16261] Enumerable#each_tuple

[daniel]

Issue #16261 has been updated by Dan0042 (Daniel DeLorme).


Note that `each{ |*item| yield(item) }` doesn't work because of #16166.

----------------------------------------
Feature #16261: Enumerable#each_tuple
https://bugs.ruby-lang.org/issues/16261#change-82243

* Author: zverok (Victor Shepelev)
* Status: Open
* Priority: Normal
* Assignee: 
* Target version: 
----------------------------------------
New method proposal.

Prototype code:
```ruby
module Enumerable
  def each_tuple
    return to_enum(__method__) unless block_given?
    each { |item| yield(*item) } # unpacking possible array into several args
  end
end
```

Supposed documentation/explanation:

> For enumerable with Array items, passes all items in the block provided as a separate arguments. t could be useful if the provided block has lambda semantics, e.g. doesn't unpack arguments automatically. For example:

  ```ruby
files = ["README.md", "LICENSE.txt", "Contributing.md"]
content = [fetch_readme, fetch_license, fetch_contributing] # somehow make a content for the files

files.zip(content).each_tuple(&File.:write) # writes to each file its content
```

> When no block passed, returns enumerator of the tuples:

  ```ruby
[1, 2, 3].zip([4, 5, 6]).each_tuple.map(&:+) # => [5, 7, 9] 
```



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

[ruby-core:95477] [Ruby master Feature#16261] Enumerable#each_tuple

[eregontp]

Issue #16261 has been updated by Eregon (Benoit Daloze).


FYI there is Enumerable#each_entry:

> Calls block once for each element in self, passing that
> element as a parameter, converting multiple values from yield to an array.

I think many methods already yield multiple arguments rather than an Array of arguments, `zip` being one of the exception.
So I'm not sure in how many cases such a method would be useful.

----------------------------------------
Feature #16261: Enumerable#each_tuple
https://bugs.ruby-lang.org/issues/16261#change-82247

* Author: zverok (Victor Shepelev)
* Status: Open
* Priority: Normal
* Assignee: 
* Target version: 
----------------------------------------
New method proposal.

Prototype code:
```ruby
module Enumerable
  def each_tuple
    return to_enum(__method__) unless block_given?
    each { |item| yield(*item) } # unpacking possible array into several args
  end
end
```

Supposed documentation/explanation:

> For enumerable with Array items, passes all items in the block provided as a separate arguments. t could be useful if the provided block has lambda semantics, e.g. doesn't unpack arguments automatically. For example:

  ```ruby
files = ["README.md", "LICENSE.txt", "Contributing.md"]
content = [fetch_readme, fetch_license, fetch_contributing] # somehow make a content for the files

files.zip(content).each_tuple(&File.:write) # writes to each file its content
```

> When no block passed, returns enumerator of the tuples:

  ```ruby
[1, 2, 3].zip([4, 5, 6]).each_tuple.map(&:+) # => [5, 7, 9] 
```



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

[ruby-core:95479] [Ruby master Feature#16261] Enumerable#each_tuple

[daniel]

Issue #16261 has been updated by Dan0042 (Daniel DeLorme).


@eregon Thank you very much for the enlightenment!

That means the code above could be rewritten like this. And at that point it's doubtful if `tuple` is even needed.

```ruby
class Enumerator
  def splat
    return to_enum(:splat) unless block_given?
    each_entry{ |item| yield(*item) }
  end
  def tuple
    return to_enum(:tuple) unless block_given?
    each_entry{ |item| yield(Array===item ? item : [item]) }
  end
end
```

----------------------------------------
Feature #16261: Enumerable#each_tuple
https://bugs.ruby-lang.org/issues/16261#change-82249

* Author: zverok (Victor Shepelev)
* Status: Open
* Priority: Normal
* Assignee: 
* Target version: 
----------------------------------------
New method proposal.

Prototype code:
```ruby
module Enumerable
  def each_tuple
    return to_enum(__method__) unless block_given?
    each { |item| yield(*item) } # unpacking possible array into several args
  end
end
```

Supposed documentation/explanation:

> For enumerable with Array items, passes all items in the block provided as a separate arguments. t could be useful if the provided block has lambda semantics, e.g. doesn't unpack arguments automatically. For example:

  ```ruby
files = ["README.md", "LICENSE.txt", "Contributing.md"]
content = [fetch_readme, fetch_license, fetch_contributing] # somehow make a content for the files

files.zip(content).each_tuple(&File.:write) # writes to each file its content
```

> When no block passed, returns enumerator of the tuples:

  ```ruby
[1, 2, 3].zip([4, 5, 6]).each_tuple.map(&:+) # => [5, 7, 9] 
```



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

[ruby-core:95483] [Ruby master Feature#16261] Enumerable#each_tuple

[duerst]

Issue #16261 has been updated by duerst (Martin Dürst).


Dan0042 (Daniel DeLorme) wrote:
> It's worth pointing out the desired difference with regards to lambdas a bit more explicitly:
> 
> ```ruby
> [1, 2, 3].zip([4, 5, 6]).map(&:+)            # ArgumentError (wrong number of arguments (given 0, expected 1))
> [1, 2, 3].zip([4, 5, 6]).each_tuple.map(&:+) # => [5, 7, 9]
> ```

What you want to do here is in many other languages done with `zip_with`:

```ruby
[1, 2, 3].zip_with([4, 5, 6], :+) # => [5, 7, 9]
```

There is already an issue for this, issue #4539, which is open and waits for Matz's approval.

----------------------------------------
Feature #16261: Enumerable#each_tuple
https://bugs.ruby-lang.org/issues/16261#change-82255

* Author: zverok (Victor Shepelev)
* Status: Open
* Priority: Normal
* Assignee: 
* Target version: 
----------------------------------------
New method proposal.

Prototype code:
```ruby
module Enumerable
  def each_tuple
    return to_enum(__method__) unless block_given?
    each { |item| yield(*item) } # unpacking possible array into several args
  end
end
```

Supposed documentation/explanation:

> For enumerable with Array items, passes all items in the block provided as a separate arguments. t could be useful if the provided block has lambda semantics, e.g. doesn't unpack arguments automatically. For example:

  ```ruby
files = ["README.md", "LICENSE.txt", "Contributing.md"]
content = [fetch_readme, fetch_license, fetch_contributing] # somehow make a content for the files

files.zip(content).each_tuple(&File.:write) # writes to each file its content
```

> When no block passed, returns enumerator of the tuples:

  ```ruby
[1, 2, 3].zip([4, 5, 6]).each_tuple.map(&:+) # => [5, 7, 9] 
```



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

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[ruby-core:95493] [Ruby master Feature#16261] Enumerable#each_tuple

[zverok.offline]

Issue #16261 has been updated by zverok (Victor Shepelev).


@duerst

> What you want to do here is in many other languages done with `zip_with`

I used `zip` only as a simplest way to construct an example. In our current codebase we have a fare share of internal methods defined with two pairs of braces, like `def similar?((word1, word2))`, because this allows us, for example, to say things like (imagine calculating some diffs):

```ruby
diff_pairs.reject(&method(:similar?)).select(&method(:same_paragraph?)).map(&method(:calculate_closeness))
```
In other places, we are still just rely on `map { |foo, bar, baz|`, `select` and so on.

A very small amount of initial data of such chains is produced with `zip`, but even when it is, `zip_with` can't help with select/reject/group_by and other Enumerable methods.

----------------------------------------
Feature #16261: Enumerable#each_tuple
https://bugs.ruby-lang.org/issues/16261#change-82264

* Author: zverok (Victor Shepelev)
* Status: Open
* Priority: Normal
* Assignee: 
* Target version: 
----------------------------------------
New method proposal.

Prototype code:
```ruby
module Enumerable
  def each_tuple
    return to_enum(__method__) unless block_given?
    each { |item| yield(*item) } # unpacking possible array into several args
  end
end
```

Supposed documentation/explanation:

> For enumerable with Array items, passes all items in the block provided as a separate arguments. t could be useful if the provided block has lambda semantics, e.g. doesn't unpack arguments automatically. For example:

  ```ruby
files = ["README.md", "LICENSE.txt", "Contributing.md"]
content = [fetch_readme, fetch_license, fetch_contributing] # somehow make a content for the files

files.zip(content).each_tuple(&File.:write) # writes to each file its content
```

> When no block passed, returns enumerator of the tuples:

  ```ruby
[1, 2, 3].zip([4, 5, 6]).each_tuple.map(&:+) # => [5, 7, 9] 
```



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

[ruby-core:96010] [Ruby master Feature#16261] Enumerable#each_splat and Enumerator#splat

[knu]

Issue #16261 has been updated by knu (Akinori MUSHA).


I agree this feature would be a nice addition.

Actually I had exactly the same idea, presented at Rails Developer Meetup 2019: https://www.slideshare.net/akinorimushaevolution-of-enumerator

There's a subtle difference between Hash#each/map and Hash#select/reject in how they yield each key-value pair.

```ruby
{a:1,b:2}.select{|x|p x}
# :a
# :b
{a:1,b:2}.each{|x|p x}
# [:a, 1]
# [:b, 2]
```

I guess this was an unintended difference, but we cannot fix it by now for compatibility reasons, and each_splat would be one way to work around it.

----------------------------------------
Feature #16261: Enumerable#each_splat and Enumerator#splat
https://bugs.ruby-lang.org/issues/16261#change-82848

* Author: zverok (Victor Shepelev)
* Status: Open
* Priority: Normal
* Assignee: 
* Target version: 
----------------------------------------
**UPD:** After discussion in comments, method names changed to "splat"-based.

New methods proposal.

Prototype code:
```ruby
module Enumerable
  def each_splat
    return to_enum(__method__) unless block_given?
    each_entry { |item| yield(*item) } # unpacking possible array into several args
  end
end

class Enumerator
  def splat
    return to_enum(:splat) unless block_given?
    each_entry { |item| yield(*item) }
  end
end
```

Supposed documentation/explanation:

> For enumerable with Array items, passes all items in the block provided as a separate arguments. t could be useful if the provided block has lambda semantics, e.g. doesn't unpack arguments automatically. For example:

  ```ruby
files = ["README.md", "LICENSE.txt", "Contributing.md"]
content = [fetch_readme, fetch_license, fetch_contributing] # somehow make a content for the files

files.zip(content).each_splat(&File.:write) # writes to each file its content
```

> When no block passed, returns enumerator of the tuples:

  ```ruby
[1, 2, 3].zip([4, 5, 6]).each_splat.map(&:+) # => [5, 7, 9] 
```



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

[ruby-core:96015] [Ruby master Feature#16261] Enumerable#each_splat and Enumerator#splat

[matz]

Issue #16261 has been updated by matz (Yukihiro Matsumoto).

Status changed from Open to Rejected

As far as I understand, the code with the proposal `[1, 2, 3].zip([4, 5, 6]).each_tuple.map(&:+)` can be written as following with numbered parameters:

```ruby
[1, 2, 3].zip([4, 5, 6]).map{_1 + _2}
```

which is quite plain and shorter. So I reject the idea for the time being. Maybe we will revisit the idea once we re-introduce the method reference operator in the future.

Matz.


----------------------------------------
Feature #16261: Enumerable#each_splat and Enumerator#splat
https://bugs.ruby-lang.org/issues/16261#change-82856

* Author: zverok (Victor Shepelev)
* Status: Rejected
* Priority: Normal
* Assignee: 
* Target version: 
----------------------------------------
**UPD:** After discussion in comments, method names changed to "splat"-based.

New methods proposal.

Prototype code:
```ruby
module Enumerable
  def each_splat
    return to_enum(__method__) unless block_given?
    each_entry { |item| yield(*item) } # unpacking possible array into several args
  end
end

class Enumerator
  def splat
    return to_enum(:splat) unless block_given?
    each_entry { |item| yield(*item) }
  end
end
```

Supposed documentation/explanation:

> For enumerable with Array items, passes all items in the block provided as a separate arguments. t could be useful if the provided block has lambda semantics, e.g. doesn't unpack arguments automatically. For example:

  ```ruby
files = ["README.md", "LICENSE.txt", "Contributing.md"]
content = [fetch_readme, fetch_license, fetch_contributing] # somehow make a content for the files

files.zip(content).each_splat(&File.:write) # writes to each file its content
```

> When no block passed, returns enumerator of the tuples:

  ```ruby
[1, 2, 3].zip([4, 5, 6]).each_splat.map(&:+) # => [5, 7, 9] 
```



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