gistfile1.rb

def future # :block:
  thread = Thread.new do
    Thread.current.abort_on_exception = false
    yield
  end
  
  lambda { thread.value }
end

def compose(proc) # :block:
  lambda { |*args| yield proc.call(*args) }
end

# Example:

f1 = future {
  (1..3).each { puts "Sleeping in #{Thread.current}..."; sleep 1 }
  next 1
}

f2 = compose(f1) { |x| x + 1 }

f3 = compose(f2) { |x| x * 2 }

puts "Waiting for result in #{Thread.current}..."
puts f3.call


# Another example (parallel HTTP fetch):

require "open-uri"

urls = ["http://echo.fruktsallad.net/?foo", "http://echo.fruktsallad.net/?bar"]

responses = urls.map { |x| future { open(x).read } }.map(&:call)

results = urls.zip(responses)
# => [["http://echo.fruktsallad.net/?foo", "foo"], ["http://echo.fruktsallad.net/?bar", "bar"]]