From: sawadatsuyoshi@... Date: 2020-09-12T14:46:58+00:00 Subject: [ruby-core:99994] [Ruby master Feature#17165] Add `filter` and `flatten` keywords to `Enumerable#map` Issue #17165 has been reported by sawa (Tsuyoshi Sawada). ---------------------------------------- Feature #17165: Add `filter` and `flatten` keywords to `Enumerable#map` https://bugs.ruby-lang.org/issues/17165 * Author: sawa (Tsuyoshi Sawada) * Status: Open * Priority: Normal ---------------------------------------- I had a use case to do `map` on an enumerable, with 1-level flattening, while skipping `nil` values. There are convenient `Enumerable#flat_map` and `Enumerable#filter_map` methods, but the problem is that they cannot be used at the same time. I had to chose to do either of the following: ```ruby array .filter_map do |foo| bar = baz(foo) next unless bar bar.map{...} end .flatten(1) ``` ```ruby array .flat_map do |foo| bar = baz(foo) next unless bar bar.map{...} end .compact ``` ```ruby array .flat_map do |foo| bar = baz(foo) next [] unless bar bar.map{...} end ``` The last one of the above may not look so bad, but it requires an extra consideration, and is a bit hacky. When you are in a hurry, it just might not come to your mind. This led me to realize that `flat_map` and `filter_map` should not be independent operations, but are rather some different modes of the operation `map`. There is no reason for the modes to be mutually exclusive of one another, and a use case that I mentioned above may arise. I propose to add `filter` and `flatten` as optional keyword arguments to `Enumerable#map`. ```ruby array .map(filter: true, flatten: 1) do |foo| bar = baz(foo) next unless bar bar.map{...} end ``` In fact, even when the two parameters are not used together, I believe it would be easier to the brain and I would feel much more comfortable to pass `filter: true` or `flatten: 1` to `map` when necessary rather than having to deicide whether to use `map` or `flat_map` or use `map` or `filter_map`. Furthermore, this would make it possible to do flattening of an arbitrary depth (as specified by the parameter) during map. -- https://bugs.ruby-lang.org/ Unsubscribe: