enumerable/lazy_value_packing.rb

tests/_examples/enumerable/lazy_value_packing.rb in the metorex repository.

# A lazy step hands on what the source yields as one value: several values
# packed into an Array, and none as nil.
pairs = Enumerator.new { |yielder| yielder.yield(1, 2) }
empty = Enumerator.new { |yielder| yielder.yield }
[:select, :reject, :take_while, :uniq].each do |step|
  walked = []
  pairs.lazy.public_send(step) { step != :reject }.each { |*values| walked << values }
  p [step, walked]
end
walked = []
empty.lazy.take(1).each { |*values| walked << values }
p walked
walked = []
pairs.lazy.with_index.each { |*values| walked << values }
p walked

# A lazy zip starts its other sources over each time it is walked.
zipped = (0..1).lazy.zip(2..3)
p zipped.force
p zipped.force

# `produce` reports an endless size, or the size it was given.
p Enumerator.produce(0) { |count| count + 1 }.size
p Enumerator.produce(0, size: -> { 5 * 5 }) { |count| count + 1 }.size
p Enumerator.produce(0, size: 3) { |count| count + 1 }.take(2)
begin
  Enumerator.produce(width: 1, depth: 2) {}
rescue ArgumentError => problem
  p problem.message
end

Output:

[:select, [[[1, 2]]]]
[:reject, [[[1, 2]]]]
[:take_while, [[[1, 2]]]]
[:uniq, [[[1, 2]]]]
[[nil]]
[[[[1, 2], 0]]]
[[0, 2], [1, 3]]
[[0, 2], [1, 3]]
Infinity
25
[0, 1]
"unknown keywords: :width, :depth"