From: Greg.mpls@... Date: 2016-08-05T13:52:02+00:00 Subject: [ruby-core:76745] [Ruby trunk Feature#12648] `Enumerable#sort_by` with descending option Issue #12648 has been updated by Greg L. Taking a step back, we are using arrays simply because that is a object that allows sorting via multiple criteria (if criteria a is equal, test with criteria b, etc). It is also my understanding that sort_by creates arrays of [enum_item, sort_value], and we are also using an array for sort_value. I'm not much for writing (or reading) c, but it would seem that a new method could use whatever structures were most efficient, regardless of the fact that arrays are used for the parameter and the block return. ---------------------------------------- Feature #12648: `Enumerable#sort_by` with descending option https://bugs.ruby-lang.org/issues/12648#change-59966 * Author: Tsuyoshi Sawada * Status: Open * Priority: Normal * Assignee: ---------------------------------------- I would like to pass an optional argument to `Enumerable#sort_by` or `Enumerable#sort_by!` to allow descending sort. When the sort key is singular, this could be done by passing a single optinal boolean variable that represents ascending when `false` (default) and descending when `true`: ```ruby [3, 1, 2].sort_by(&:itself) # => [1, 2, 3] [3, 1, 2].sort_by(false, &:itself) # => [1, 2, 3] [3, 1, 2].sort_by(true, &:itself) # => [3, 2, 1] ``` When there are multiple sort keys, corresponding numbers of arguments should be passed: ```ruby [3, 1, 2, 0].sort_by{|e| [e % 2, e]} # => [0, 2, 1, 3] [3, 1, 2, 0].sort_by(false, false){|e| [e % 2, e]} # => [0, 2, 1, 3] [3, 1, 2, 0].sort_by(false, true){|e| [e % 2, e]} # => [2, 0, 3, 1] [3, 1, 2, 0].sort_by(true, false){|e| [e % 2, e]} # => [1, 3, 0, 2] [3, 1, 2, 0].sort_by(true, true){|e| [e % 2, e]} # => [3, 1, 2, 0] ``` -- https://bugs.ruby-lang.org/ Unsubscribe: