From: Yehuda Katz <wycats@...>
Date: 2011-11-23T05:37:33+09:00
Subject: [ruby-core:41213] [ruby-trunk - Bug #5663][Open] Combined map/select method


Issue #5663 has been reported by Yehuda Katz.

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Bug #5663: Combined map/select method
http://redmine.ruby-lang.org/issues/5663

Author: Yehuda Katz
Status: Open
Priority: Normal
Assignee: 
Category: 
Target version: 
ruby -v: ruby 1.9.3p0 (2011-11-08 revision 33661) [x86_64-darwin11.2.0]


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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