[ruby-core:117199] [Ruby master Feature#19787] Add Enumerable#uniq_map, Enumerable::Lazy#uniq_map, Array#uniq_map and Array#uniq_map!

["joshuay03 (Joshua Young) via ruby-core" <ruby-core@ml.ruby-lang.org>]

Issue #19787 has been updated by joshuay03 (Joshua Young).


rubyFeedback (robert heiler) wrote in #note-6:

> Ultimately you only have to convince matz. :)
> 
> However had, matz may also request additional information and/or use case and
> "usefulness" of suggestions. Once features are added it is difficult to remove
> them due to backwards compatibility.

Thanks, that's a good point re: backwards compatibility.

> I am not really invested in the proposal here, so I will not comment much at
> all. The way how I use ruby I use .map {} a lot, and .uniq sometimes, but I 
> don't think I really had major use cases for combining the above into one 
> method call. Note that I also don't use .flat_map either - I kind of prefer
> to stay with one-word methods when possible. They seem to make more sense to
> my brain. (I understand a rationale for e. g. library authors where efficiency
> may be more important, but personally I use ruby as kind of "syntax sugar"
> over C, the operating system and everyday tasks - ruby is really like the 
> ultimate glue language the way how I use it. But that's just a side comment,
> I completely understand different people using ruby differently; just for my
> own use cases I don't seem to need .uniq_map or .flat_map. By the way, I also
> find it harder to remember the method names for two-word methods, e. g. 
> .map_uniq or .map_flat; that's also one reason I stick with oldschool method
> chaining. Perhaps I am getting old ... .lazy is a bit different in that it
> also defers using something at "when it is needed", along with the functional
> use cases it has, which I think is different to both .flat_map and .uniq_map.)

I appreciate the feedback.

----------------------------------------
Feature #19787: Add Enumerable#uniq_map, Enumerable::Lazy#uniq_map, Array#uniq_map and Array#uniq_map!
https://bugs.ruby-lang.org/issues/19787#change-107288

* Author: joshuay03 (Joshua Young)
* Status: Open
----------------------------------------
I would like to propose a collection of new methods, `Enumerable#uniq_map`, `Enumerable::Lazy#uniq_map`, `Array#uniq_map` and `Array#uniq_map!`.

TL;DR: It's a drop in replacement for `.map { ... }.uniq`, with (hopefully) better performance.

I've quite often had to map over an array and get its unique elements. It occurred to me when doing so recently that Ruby doesn't have a short form method for doing that, similar to how `.flat_map { ... }` replaces `.map { ... }.flatten` and `.filter_map { ... }` replaces `.map { ... }.compact` (with minor differences). I think these new methods could be beneficial both in terms of better performance and writing more succinct code.

I've got a draft PR up with some initial benchmarks in the description: https://github.com/ruby/ruby/pull/10269.



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