From: "rosenfeld (Rodrigo Rosenfeld Rosas)" <rr.rosas@...>
Date: 2012-04-01T11:18:16+09:00
Subject: [ruby-core:44034] [ruby-trunk - Feature #5663] Combined map/select method


Issue #5663 has been updated by rosenfeld (Rodrigo Rosenfeld Rosas).


I actually prefer map_select as it is self-explanatory. There isn't a single word that is able to clearly provide the description for what it does.
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Feature #5663: Combined map/select method
https://bugs.ruby-lang.org/issues/5663#change-25563

Author: wycats (Yehuda Katz)
Status: Feedback
Priority: Normal
Assignee: matz (Yukihiro Matsumoto)
Category: lib
Target version: 2.0.0


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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