Feature #12075: some container#nonempty?

• Status: Feedback
• Priority: Normal
• Assignee: matz (Yukihiro Matsumoto)
• Target version: -

[naruse (Yui NARUSE)]

I sometimes write following code.

ary = some_metho_returns_nil_or_empty_container() # nil or "" or [] or {}

if ary && !ary.empty?
  #  some code
end

But the condition ary && !ary.empty? is too long and complex.
Though Ruby 2.3 introduces &., but this can’t be written as ary&.empty?.

One idea is add nonempty? write as ary&.nonempty?.

akr: nonempty? is not good name because human is not good at handling

This discussion matches following core classes:

• String
• Array
• Hash

[mrkn (Kenta Murata)]

How about ary.include_something? ?

[akr (Akira Tanaka)]

How about "some?".

[sawa (Tsuyoshi Sawada)]

That is a use case for Rails' blank? (or present?).

class Object
  def blank?
    respond_to?(:empty?) ? !!empty? : !self
  end
end

unless ary.blank?
  #  some code
end

What about incorporating these methods from Rails?

[rosenfeld (Rodrigo Rosenfeld Rosas)]

+1 for bringing blank? and present? to Ruby core. I often use (a || '').empty? checks for not having to depend on ActiveSupport directly in my Ruby code. I'd love to see them in Ruby core though.

[shyouhei (Shyouhei Urabe)]

No, the OP wants to detect things that are not empty. This is not what blank? means. Also note that blank? in ActiveSupport has different (far more Rails-centric) semantics than what is described in #3.

https://github.com/rails/rails/blob/b3eac823006eb6a346f88793aabef28a6d4f928c/activesupport/lib/active_support/core_ext/object/blank.rb#L115

[sawa (Tsuyoshi Sawada)]

Shyouhei Urabe wrote:

No, the OP wants to detect things that are not empty. This is not what blank? means.

Yes, I meant that blank? is the opposite of what OP wants. present? is what the OP wants. I replaced if in the original example with unless, so it is the same (Or, to retain if, present? can be used).

ActiveSupport has different (far more Rails-centric) semantics than what is described in #3.

I see.

[rosenfeld (Rodrigo Rosenfeld Rosas)]

The implementation doesn't have to be the same as the one implemented by ActiveSupport. I think it would be fine to simply check for nil? and empty?. But I'd like to keep the names present? and blank? anyway.

[shevegen (Robert A. Heiler)]

Perhaps the name .contains? might be good?

Although, .include? sort of is more or less synonymous with .contains? so perhaps this is not a good choice either.

.nonempty? seems a bit long, .non_empty? would be even longer :)

.empty? is a very good name already, I am not sure if "! .empty?" has a good name, though ruby uses the keyword "not"
already. Could use .notempty? haha sorry, I have no good suggestion for a fitting name for negation either, but I am
totally fine with the idea and functionality of the proposal itself, it's a good one.

[shyouhei (Shyouhei Urabe)]

I have just learned that zsh(1) calls this concept being "full". http://zsh.sourceforge.net/Doc/Release/Expansion.html#Glob-Qualifiers

[sawa (Tsuyoshi Sawada)]

What about introducing NilClass#empty?:

nil.empty? # => true

The code in question can be written simply as:

unless ary.empty?
  #  some code
end

If the original proposal is going to be realized, then a new method would have to be added to NilClass, String, Array, and Hash, but my proposal makes use of the existing method empty?, and needs to add to only NilClass, keeping the change minimal.

Even if the original proposal is going to be realized, extending empty? as above would make it the complete opposite of such method, and would introduce parallelism.

[rosenfeld (Rodrigo Rosenfeld Rosas)]

I like this idea a lot, Tsuyoshi. I'm +1 for introducing nil.empty? as returning true.

[nobu (Nobuyoshi Nakada)]

First, along this line, we'll need negative forms for all predicate methods.

And I think nil.empty? makes no sense.

Just an idea:

module Kernel
  def not(*a)
    not a.empty? ? self : __send__(*a)
  end
end

ary = nil;   ary&.not(:empty?) #=> nil
ary = [];    ary&.not(:empty?) #=> false
ary = [nil]; ary&.not(:empty?) #=> true

[nobu (Nobuyoshi Nakada)]

Or

module Kernel
  def !(*a)
    a.empty? ? super() : !__send__(*a)
  end
end

ary = nil;   ary&.!:empty? #=> nil
ary = [];    ary&.!:empty? #=> false
ary = [nil]; ary&.!:empty? #=> true

[phluid61 (Matthew Kerwin)]

Nobuyoshi Nakada wrote:

First, along this line, we'll need negative forms for all predicate methods.

And I think nil.empty? makes no sense.

Just an idea:

module Kernel
  def not(*a)
    not a.empty? ? self : __send__(*a)
  end
end

ary = nil;   ary&.not(:empty?) #=> nil
ary = [];    ary&.not(:empty?) #=> false
ary = [nil]; ary&.not(:empty?) #=> true

I like this proposal. I definitely prefer the word 'not' over the symbol '!', because ary&.!:empty? has too much consecutive punctuation for my eyes.

Would there be value in extending it to accept a block?

module Kernel
  def not(*a, &b)
    not a.empty? ? self : __send__(*a, &b)
    # or even:
    #not a.empty? ? (b ? (yield self) : self) : __send__(*a, &b)
  end
end

ary = [];  ary&.not(:any?){|x|x>0} #=> true
ary = [1]; ary&.not(:any?){|x|x>0} #=> false

[nobu (Nobuyoshi Nakada)]

https://github.com/ruby/ruby/compare/trunk...nobu:feature/12075-not

[Eregon (Benoit Daloze)]

Nobuyoshi Nakada wrote:

https://github.com/ruby/ruby/compare/trunk...nobu:feature/12075-not

I like it!

[nobu (Nobuyoshi Nakada)]

• Description updated (diff)

[naruse (Yui NARUSE)]

• Status changed from Assigned to Feedback

Array#any? seems to work usual use cases.
Feedback if another cases are discovered.

[sorah (Sorah Fukumori)]

I know any? works on some use cases, but I'm positive to have a proposed method because using any? has a pitfall. We have to guarantee an array doesn't have only false or nil. Also I'm worrying users who started to use any? for this use case, but doesn't know this pitfall.

I'm positive on Object#not idea.

[nobu (Nobuyoshi Nakada)]

• Related to Feature #13395: Add a method to check for not nil added

[nobu (Nobuyoshi Nakada)]

• Related to Feature #17330: Object#non added

[mame (Yusuke Endoh)]

I like Array#some? and Hash#some?. It is so frequent to write !ary.empty?.

I think the main concern is only about empty?, not other predicate methods. So I'm skeptical about the need of the generalization like ary.not(:empty?). I don't like it very much because it is longer and slower than the dedicated method.

[sawa (Tsuyoshi Sawada)]

I want to mention that some of the method names proposed so far would break symmetry.

Note that "empty" is a property of the container, not the elements. When you have a = [1], what is questioned whether it is empty or not is a, but not 1. Among the words proposed so far, "any" and "some" are not a property of the container, but are a word used together with the elements, e.g., "some element 1". "present" in this respect is also not appropriate because it is a property of the element ("1 is present"), not the container (not "a is present"). If the method in question is to be defined as the negation of empty?, then its name should be a property of the container.

Among the words proposed so far, "non-empty", "not empty", and "full" would work. Another word that comes to mind is "occupied", but it may be too long.