[#100689] [Ruby master Feature#17303] Make webrick to bundled gems or remove from stdlib — hsbt@...
Issue #17303 has been reported by hsbt (Hiroshi SHIBATA).
11 messages
2020/11/02
[#100852] [Ruby master Feature#17326] Add Kernel#must! to the standard library — zimmerman.jake@...
SXNzdWUgIzE3MzI2IGhhcyBiZWVuIHJlcG9ydGVkIGJ5IGpleiAoSmFrZSBaaW1tZXJtYW4pLg0K
24 messages
2020/11/14
[#100930] [Ruby master Feature#17333] Enumerable#many? — masafumi.o1988@...
Issue #17333 has been reported by okuramasafumi (Masafumi OKURA).
10 messages
2020/11/18
[#101071] [Ruby master Feature#17342] Hash#fetch_set — hunter_spawn@...
Issue #17342 has been reported by MaxLap (Maxime Lapointe).
26 messages
2020/11/25
[ruby-core:101156] [Ruby master Feature#17016] Enumerable#scan_left
From:
finch.parker@...
Date:
2020-11-30 14:38:03 UTC
List:
ruby-core #101156
Issue #17016 has been updated by parker (Parker Finch). y.annikov (Yakov Annikov) wrote in #note-35: > What about `#cumulate`? Does it sound natural? I'm not as familiar with the verb "cumulate", so it doesn't sound as natural to me as "accumulate". But that being said, I don't think there's a huge difference between the two words, so either one could work! ---------------------------------------- Feature #17016: Enumerable#scan_left https://bugs.ruby-lang.org/issues/17016#change-88842 * Author: parker (Parker Finch) * Status: Open * Priority: Normal ---------------------------------------- ## Proposal Add a `#scan_left` method to `Enumerable`. (The name "scan_left" is based on Scala's scanLeft and Haskell's scanl. It seems like "scan_left" would be a ruby-ish name for this concept, but I'm curious if there are other thoughts on naming here!) ## Background `#scan_left` is similar to `#inject`, but it accumulates the partial results that are computed. As a comparison: ``` [1, 2, 3].inject(0, &:+) => 6 [1, 2, 3].scan_left(0, &:+) => [0, 1, 3, 6] ``` Notably, the `scan_left` operation can be done lazily since it doesn't require processing the entire collection before computing a value. I recently described `#scan_left`, and its relationship to `#inject`, more thoroughly in [this blog post](https://medium.com/building-panorama-education/scan-left-a-lazy-incremental-alternative-to-inject-f6e946f74c00). ## Reasoning We heavily rely on the scan operation. We use an [event-sourcing](https://martinfowler.com/eaaDev/EventSourcing.html) pattern, which means that we are scanning over individual "events" and building up the corresponding state. We rely on the history of states and need to do this lazily (we stream events because they cannot fit in memory). Thus the scan operation is much more applicable than the inject operation. We suspect that there are many applications that could leverage the scan operation. [This question](https://stackoverflow.com/questions/1475808/cumulative-array-sum-in-ruby) would be more easily answered by `#scan_left`. It is a natural fit for any application that needs to store the incrementally-computed values of an `#inject`, and a requirement for an application that needs to use `#inject` while maintaining laziness. ## Implementation There is a Ruby implementation of this functionality [here](https://github.com/panorama-ed/scan_left/) and an implementation in C [here](https://github.com/ruby/ruby/pull/3078). ## Counterarguments Introducing a new public method is committing to maintenance going forward and expands the size of the Ruby codebase -- it should not be done lightly. I think that providing the functionality here is worth the tradeoff, but I understand any hesitation to add yet more to Ruby! ---Files-------------------------------- scan_left_example.rb (2.93 KB) -- https://bugs.ruby-lang.org/ Unsubscribe: <mailto:[email protected]?subject=unsubscribe> <http://lists.ruby-lang.org/cgi-bin/mailman/options/ruby-core>