From: takashikkbn@...
Date: 2017-06-29T01:07:45+00:00
Subject: [ruby-core:81821] [Ruby trunk Feature#13692] Array#index?

Issue #13692 has been updated by k0kubun (Takashi Kokubun).


~~~ ruby
def from(index)
  if index?(index)
     self[index..-1]
  else
    []
  end
end
~~~

Not considered well, but wouldn't it be sufficient to use following simple implementation?

~~~ ruby
def from(index)
  self[index..-1] || []
end
~~~

And first of all, I couldn't imagine the use case to use such Array#from with large negative index too.

----------------------------------------
Feature #13692: Array#index?
https://bugs.ruby-lang.org/issues/13692#change-65516

* Author: se8 (S��bastien Durand)
* Status: Open
* Priority: Normal
* Assignee: 
* Target version: 
----------------------------------------
Hello!

We currently have these methods:

~~~
Hash#key(value)
Hash#key?(key)
Array#index(value)
~~~

I was thinking we could add this tiny method:

~~~
Array#index?(index)
~~~

as this is sometimes useful to check if an array index exists.



~~~ ruby
class Array

  def index?(index)
    index.between?(0 - size, size - 1)
  end

end

['a', 'b', 'c'].index?(0) # => true
['a', 'b', 'c'].index?(2) # => true
['a', 'b', 'c'].index?(3) # => false
['a', 'b', 'c'].index?(-1) # => true
['a', 'b', 'c'].index?(-3) # => true
['a', 'b', 'c'].index?(-4) # => false
[false, nil].index?(0) #=> true
[false, nil].index?(1) #=> true
~~~




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