Issue #5663 has been updated by Joshua Ballanco.


What about using "next" for this purpose? Currently:

> (1..10).to_a.map { |i| i % 3 == 0 ? next : i**2 }
 => [1, 4, nil, 16, 25, nil, 49, 64, nil, 100]

Is it so common to use "next" with a return value inside of an Enumerable#map call? Even so, could we special case "next" so that instead of returning nil, it skips the element entirely?
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Feature #5663: Combined map/select method
https://bugs.ruby-lang.org/issues/5663

Author: Yehuda Katz
Status: Assigned
Priority: Normal
Assignee: 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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