channels

# Channels: tasks talk by sending values, not by sharing them.

jobs = Channel(Int32).new(8)
results = Channel(Int32).new(8)

group do |g|
  # Two workers. Each takes jobs until the channel closes.
  2.times do
    g.spawn do
      loop do
        case jobs.receive
        in Int32         then results.send(it * 10)
        in ChannelClosed then break
        in Cancelled     then break
        end
      end
      0
    end
  end

  # One producer. Closing says there will be no more.
  g.spawn do
    (1..5).each { |n| jobs.send(n) }
    jobs.close
    0
  end

  # Collect five answers.
  total = 0
  5.times do
    case results.receive
    in Int32         then total += it
    in ChannelClosed then break
    in Cancelled     then break
    end
  end
  puts total
end