From: marcandre-ruby-core@... Date: 2020-05-06T16:44:15+00:00 Subject: [ruby-core:98153] [Ruby master Feature#16833] Add Enumerator#empty? Issue #16833 has been updated by marcandre (Marc-Andre Lafortune). Enumerators can behave very differently than arrays. Some have side-effects. What's supposed to happen with those? ``` require 'stringio' s = StringIO.new("first\nsecond\nthird\nlast").each_line s.first # => "first" s.first # => "second" s.empty? # => false s.first # => "third" or "last"? s.empty? # => false or true? ``` You may want to rethink your algorithm, or simply call `to_a` once and act on the array. For similar reasons, `Enumerator#size` exist and is lazy, but it may return `nil` (e.g. `s.size` above) so wouldn't completely serve your purpose either. For these reason I think you should either close your request or elaborate on an actual use case where a generic enumerator is being used, as well as the actual effect of `empty?` on external iterators, ... ---------------------------------------- Feature #16833: Add Enumerator#empty? https://bugs.ruby-lang.org/issues/16833#change-85393 * Author: f3ndot (Justin Bull) * Status: Open * Priority: Normal ---------------------------------------- It was surprising to me that Enumerator, something mixed into Array, does not include `#empty?`. I think it is reasonable to assume people may have to guard iterating and other logic based on the emptiness of an enumerator, such was my case. ``` ruby # pretend there's convoluted enumerator logic to produce this structure table_rows = [{ data: ['First', 'Second', 'Third'], config: {} }, { data: [4, 5, 6], config: { color: 'red' } }].to_enum return if table_rows.empty? table_header = table_rows.first[:data] # requires an empty guard # ... ``` I propose that it simply behaves as `#take(1).to_a.empty?` instead of aliasing to something like `#none?` because of falsey elements or `#size == 0` because of potential `nil` returns: ```ruby [].to_enum.empty? # => true [false].to_enum.empty? # => false [nil].to_enum.empty? # => false [0].to_enum.empty? # => false [1, 2, 3].to_enum.empty? # => false ``` ---Files-------------------------------- add-enumerable-empty.patch (1.99 KB) -- https://bugs.ruby-lang.org/ Unsubscribe: