[GitHub] [beam] GodefroyClair opened a new issue, #25807: Why is FlatMap not Flatten + Map?

["GodefroyClair (via GitHub)" <gi...@apache.org>]

GodefroyClair opened a new issue, #25807:
URL: https://github.com/apache/beam/issues/25807

   Maybe I'm not asking at the right place but I am quite surprised about the way `Flatten()` and `FlatMap()` are implemented in Python.
   Normally, in functional progamming (Haskell, Scala...), FlatMap() should be the same as composing `Flatten()` and `Map()`.
   But in Apache Beam, Flatten() is using _iterable of PCollections_ while FlatMap() is working with _PCollection of Iterables_.
   
   ```
   Flatten:: Iterable[PCollections[A]] -> PCollection[A]
   Map:: (PCollection[A], (A-> B)) -> PCollection[B]
   
   FlatMap:: (PCollection[Iterable[A]], (A->B)) -> [A]
   ```
   
   So my question is is there another Flatten with this signature :
   anotherFlatten:: PCollection[Iterable[A]] -> PCollection[A]
   
   One of the reason this would be useful, is that when you just want to use `Flatten` a `PCollection` of `iterable` you have to use `FlatMap()`with an identity function (for example to use empty list as an alternative to the [Maybe/Optional Monad](https://blog.ploeh.dk/2022/04/25/the-maybe-monad/) Pattern)
   
   So instead of writing:
   `FlatMap(lambda e: e)`
   I would like to have a function
   `anotherFlatten()`
   
   Plus this is not helping when you are trying to teach functional programming with Apache Beam to Pythonist... it kinds of break the intuition about FlatMap.


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[GitHub] [beam] aromanenko-dev closed issue #25807: Why is FlatMap different from composing Flatten and Map?

["aromanenko-dev (via GitHub)" <gi...@apache.org>]

aromanenko-dev closed issue #25807: Why is FlatMap different from composing Flatten and Map?
URL: https://github.com/apache/beam/issues/25807


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[GitHub] [beam] aromanenko-dev commented on issue #25807: Why is FlatMap different from composing Flatten and Map?

["aromanenko-dev (via GitHub)" <gi...@apache.org>]

aromanenko-dev commented on issue #25807:
URL: https://github.com/apache/beam/issues/25807#issuecomment-1466275172

   Since it's not an issue and just a question for discussion, could you ask this on [user@beam.apache.org](https://lists.apache.org/list.html?user@beam.apache.org)?
   Thanks!


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