This page contains automated test results for code from O'Reilly's Ruby Cookbook. If this code looks interesting or useful, you might want to buy the whole book.

Looping Through Multiple Iterables in Parallel
CodeExpectedActual
require 'generator'
enumerator = SyncEnumerator.new(%w{Four seven}, %w{score years}, 
            	                %w{and ago})
enumerator.each do |row|
  row.each { |word| puts word }
  puts '---'
end
 
Four
score
and
---
seven
years
ago
---
 
Four
score
and
---
seven
years
ago
---
 
enumerator = SyncEnumerator.new(%w{Four and}, %w{score seven years ago})
enumerator.each do |row|
  row.each { |word| puts word }
  puts '---'
end
 
Four
score
---
and
seven
---
nil
years
---
nil
ago
---
 
Four
score
---
and
seven
---
nil
years
---
nil
ago
---
 
def interosculate(*enumerables)
  generators = enumerables.collect { |x| Generator.new(x) }
  done = false
  until done	
    done = true
    generators.each do |g|
      if g.next?
        yield g.next
        done = false
      end
    end
  end
end
interosculate(%w{Four and}, %w{score seven years ago}) do |x|
  puts x
end
 
Four
score
and
seven
years
ago
 
Four
score
and
seven
years
ago
 
l = ["junk1", 1, "junk2", 2, "junk3", "junk4", 3, "junk5"]
g = Generator.new(l)
g.next
 "junk1" "junk1" 
g.next
 1 1 
g.next
 "junk2" "junk2" 
def l.my_iterator
  each { |e| yield e unless e =~ /^junk/ }
end
l.my_iterator { |x| puts x }
 
1
2
3
 
1
2
3
 
g = Generator.new { |g| l.each { |e| g.yield e unless e =~ /^junk/ } }
g.next
 1 1 
g.next
 2 2 
g.next
 3 3 
g = Generator.new { |g| l.my_iterator { |e| g.yield e } }
g.next
 1 1 
g.next
 2 2 
g.next
 3 3 
def interosculate(*iteratables)
  generators = iteratables.collect do |x| 
    if x.is_a? Method
      Generator.new { |g| x.call { |e| g.yield e } }
    else
      Generator.new(x) 
    end
  end
  done = false
  until done	
    done = true
    generators.each do |g|
      if g.next?
        yield g.next
        done = false
      end
    end
  end
end
words1 = %w{Four and years}
words2 = %w{ago seven score}
interosculate(words1, words2.method(:reverse_each)) { |x| puts x }
 
Four
score
and
seven
years
ago
 
Four
score
and
seven
years
ago