Feature #6532: More methods for Hash and Array: Hash#has_all_keys? and family, Array#delete_at for multiple arguments

• Status: Rejected
• Assignee: -
• Target version: -

[prijutme4ty (Ilya Vorontsov)]

I suggest introducing Hash methods: has_all_keys?, has_any_key?, has_none_key?, has_one_key?
to write: input.has_all_keys? %w{A C G T}
instead of: %w{A C G T}.all?{|letter| input.has_key? letter}

and to write args.has_one_key?(:input_file, :input_string, :input_from_another_source, ...) instead of obvious but verbose code with iterating through keys

Also I suggest reimplement method Array#delete_at to work with multiple keys:
def delete_at(*args)
args.sort.reverse{|index| current_version_of_delete_at index}
end

It helps not only writing multiple deletion code faster but also prevents mistakes with deleting elements from an array in arbitrary order

[prijutme4ty (Ilya Vorontsov)]

And of course I forgot the most useful method (more suggestions about names highly appreciate) Array#selection and Hash#selection

alphabet = %w{a b c d e f g h i j}
alphabet.selection(0,1,5,7) # ==> ['a','b','f','h']
{A: 1, T: 4, G: 3, C: 5}.selection(:A,:C,:G,:T) # => [1,5,3,4]

I have several unsolved issues:
1)what's the proper name for a method;
2)whether this method should return array or enumerator
3) whether it should work with block like #map:
{A: 1, T: 4, G: 3, C: 5}.selection(:A,:C,:G,:T){|el| el.to_f} # => [1.0, 5.0, 3.0, 4.0]
or like #each
{A: 1, T: 4, G: 3, C: 5}.selection(:A,:C,:G,:T){|el| print el} # => 1534

[Eregon (Benoit Daloze)]

You should have a look at #values_at about #selection.

I'm against has_*_keys?, because I think using any?,all?,... is clearer and not too verbose. (If it did look like C with an explicit loop, then I would consider it verbose).

About #delete_at with multiple arguments, I'm neutral, because this is inherently inefficient because all the elements after the index being deleted need to be moved, at every single deletion. A Set might be more appropriate in these circumstances.

[marcandre (Marc-Andre Lafortune)]

• Status changed from Open to Rejected

I've written a short wiki on making feature requests: http://bugs.ruby-lang.org/projects/ruby/wiki/HowToRequestFeatures
I'm inviting others to review and edit it...

I'm rejecting this feature request as it contains many different requests. Besides most of them appear to have been poorly thought out and researched. Please open new requests for those you still feel confident about, bearing in mind that:

• your selection is probably not useful given values_at
• your ruby implementation of delete_at is probably not what you meant (unless you meant that arr.delete_at(0,0,0) would delete the first, second and third element and that you didn't think about the return value of delete_at, which makes it unreasonable to extend how you request it
• you need to build a solid case for you has__keys? as there are many simple alternatives (e.g. using sets, (h.keys & %w[A C G T]).empty?, h.values_at(%w[A C G T]).any? ...)