From: shugo@...
Date: 2014-03-03T12:04:09+00:00
Subject: [ruby-core:61255] [ruby-trunk - Feature #5663] [Assigned] Combined	map/select method

Issue #5663 has been updated by Shugo Maeda.

Status changed from Feedback to Assigned

Yukihiro Matsumoto wrote:
> I am OK with the original map_select behavior, but I don't like the name #map_select.
> It is combination of -ect family name with map.
> 
> I prefer the name #filter, but it might be confused by simple alias of select.
> Any idea?

What do you think of the following counter proposals?

* select_yield
* filter_map
* map_if

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Feature #5663: Combined map/select method
https://bugs.ruby-lang.org/issues/5663#change-45595

* Author: Yehuda Katz
* Status: Assigned
* Priority: Normal
* Assignee: Yukihiro Matsumoto
* Category: lib
* Target version: next minor
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It is pretty common to want to map over an Enumerable, but only include the elements that match a particular filter. A common idiom is:

enum.map { |i| i + 1 if i.even? }.compact

It is of course also possible to do this with two calls:

enum.select { |i| i.even? }.map { |i| i + 1 }

Both cases are clumsy and require two iterations through the loop. I'd like to propose a combined method:

enum.map_select { |i| i + 1 if i.even? }

The only caveat is that it would be impossible to intentionally return nil here; suggestions welcome. The naming is also a strawman; feel free to propose something better.



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