[ruby-core:114321] [Ruby master Feature#19787] Add Enumerable#uniq_map, Enumerable::Lazy#uniq_map, Array#uniq_map and Array#uniq_map!

Issue #19787 has been updated by rubyFeedback (robert heiler).


joshuay03 wrote:

> What is the usual process for deciding on whether or not to accept a feature?

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.

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.)


----------------------------------------
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-104021

* Author: joshuay03 (Joshua Young)
* Status: Open
* Priority: Normal
----------------------------------------
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/8140.



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