[ruby-dev:47050] [ruby-trunk - Feature #7877] E::Lazy#with_index needed

Issue #7877 has been updated by marcandre (Marc-Andre Lafortune).


Note that (thanks to #7715), you can use `with_index` without a block and follow it with `map`:

    def leibniz(n)
      (0..Float::INFINITY).lazy.with_index.map {|i, j| (-1 ** j) / (2*i+1).to_f }.take(n).reduce(:+)
    end

I'm neutral about this feature request. The problem I see is that it's too late for 2.0.0 and it would introduce potential incompatibility in next minor.
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Feature #7877: E::Lazy#with_index needed
https://bugs.ruby-lang.org/issues/7877#change-36623

Author: shyouhei (Shyouhei Urabe)
Status: Assigned
Priority: Normal
Assignee: yhara (Yutaka HARA)
Category: core
Target version: next minor


=begin
So I wanted some real benefit of being lazy.  I wrote a Leibniz formula:

  def leibniz(n)
    (0..Float::INFINITY).lazy.with_index {|i, j| (-1 ** j) / (2*i+1).to_f }.take(n).reduce(:+)
  end

But it doesn't work (well, it does, indeed. It just doesn't stop working).  I got frustrated.
How about it?  Don't you feel it nifty?

Of course I can wait for the release next to 2.0.0.
=end


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