Feature #16833
openAdd Enumerable#empty?
Description
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.
# 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:
[].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
Updated by f3ndot (Justin Bull) over 4 years ago
- File add-enumerable-empty.patch add-enumerable-empty.patch added
- Description updated (diff)
Updated by sawa (Tsuyoshi Sawada) over 4 years ago
Not sure what you mean by
Enumerator, something mixed into Array
Do you mean this?
Enumerator, which is mixed into Array
If that was what you meant, then that is not the case. Array
mixes-in Enumerable
, not Enumerator
.
Even if that was the case, it is not clear how that is relevant to your argument. Array
has its own empty?
method, so even if its ancestor had an empty?
method, the latter would be overridden by the former.
Updated by sawa (Tsuyoshi Sawada) over 4 years ago
Your use case is not clear. Why can't you do this?
table_rows = [{ data: ['First', 'Second', 'Third'], config: {} }, { data: [4, 5, 6], config: { color: 'red' } }].to_enum
table_rows.to_a.dig(0, :data) # => ["First", "Second", "Third"]
table_rows = [].to_enum
table_rows.to_a.dig(0, :data) # => nil
I don't understand why you need to conditionally return as in your code.
Updated by marcandre (Marc-Andre Lafortune) over 4 years ago
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, ...
Updated by shevegen (Robert A. Heiler) over 4 years ago
sawa wrote:
If that was what you meant, then that is not the case. Array mixes-in
Enumerable, not Enumerator.
Happens to me as well a lot - I always mix these two up. May be because
the name is so similar. :)
To the suggestion itself: I have no particular preference either way so
I won't really comment on the proposal itself.
Updated by ioquatix (Samuel Williams) over 1 year ago
- Assignee set to ioquatix (Samuel Williams)
Updated by ioquatix (Samuel Williams) over 1 year ago
- Subject changed from Add Enumerator#empty? to Add Enumerable#empty?
Updated by hsbt (Hiroshi SHIBATA) 7 months ago
- Status changed from Open to Assigned