From: "dsisnero (Dominic Sisneros)" <dsisnero@...>
Date: 2012-08-22T04:42:05+09:00
Subject: [ruby-core:47265] [ruby-trunk - Feature #6824] StopIteration gets a source method


Issue #6824 has been updated by dsisnero (Dominic Sisneros).


 I use the following method to weave enumerators together

#Intersperse several iterables, until all are exhausted
    def weave(*enumerators)
      enums = enumerators.map{|e| e.to_enum}    
      result = Enumerator.new do |y|     
        while !enums.empty?
          loop_enum = enums.dup
          loop_enum.each_with_index do |enum,i|
            begin
              y << enum.next
            rescue StopIteration
              #raise StopIteration if enums.empty?
              enums.delete_at(i)
            end
          end
        end
        #raise StopIteration
      end
    end  
----------------------------------------
Feature #6824: StopIteration gets a source method
https://bugs.ruby-lang.org/issues/6824#change-28961

Author: jasiek (Jan Szumiec)
Status: Open
Priority: Normal
Assignee: 
Category: core
Target version: 2.0.0


=begin
I'd like to add a method to StopIteration that returns an instance of the enumerator which triggered this exception. Eg:

  enum = [].each
  begin
    enum.next
  rescue StopIteration => ex
    puts "same" if ex.source == enum
  end

This is useful when you're merging multiple collections using min/max - when one of the collections is exhausted it can be easily ignored.

  enumerators = 100.times.map do
    rand(100).times.map do
      rand
    end.sort.each
  end

  merged = []
  while !enumerators.empty?
    begin
      enumerators.map(&:peek)
      values = enumerators.map(&:next)

      merged += values.sort
    rescue StopIteration => e
      enumerators.delete(e.source)
      retry
    end
  end

  fail unless merged != merged.sort

Attached is a patch against trunk.
=end




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