From: Greg.mpls@... Date: 2016-08-05T13:01:18+00:00 Subject: [ruby-core:76744] [Ruby trunk Feature#12648] `Enumerable#sort_by` with descending option Issue #12648 has been updated by Greg L. Nobuyoshi Nakada wrote: > Greg L wrote: > > Hence, a better solution might be adding a method like `sort_keys` or `sort_key`, where an array is returned by the block, and an array is used as the single parameter for ascending/descending info. > > Could you make clear what object these `sort_key`/`sort_keys` methods belong to? > The array to be sorted? > Or the returned object (it may not be an array) from the block? I mentioned the fact that an array is often not returned by the block, hence, my suggestion for adding a new method. Sorry, I should have shown a signature, below would be a possibility. The example shows three sort keys, 1st and 3rd are ascending, 2nd is descending. `t = enum.sort_key([1, -1, 1]) { |x| [f(x), g(x), h(x)] }` > Do you mean `enum.sort_by(-1) {...}` for descending? Yes, but in an array, as above. IOW, both the block return and the single parameter must be arrays. ---------------------------------------- Feature #12648: `Enumerable#sort_by` with descending option https://bugs.ruby-lang.org/issues/12648#change-59965 * 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: