class Proc

def <<(g)
  if lambda?
    lambda { |*args, &blk| call(g.call(*args, &blk)) }
  else
    proc { |*args, &blk| call(g.call(*args, &blk)) }
  end
end

def >>(g)
  if lambda?
    lambda { |*args, &blk| g.call(call(*args, &blk)) }
  else
    proc { |*args, &blk| g.call(call(*args, &blk)) }
  end
end

def curry(argc = nil)
  min_argc = arity < 0 ? -arity - 1 : arity
  argc ||= min_argc
  if lambda? and arity < 0 ? argc < min_argc : argc != arity
    raise ArgumentError, "wrong number of arguments (#{argc} for #{min_argc})"
  end
  creator = lambda? ? :lambda : :proc
  block = send(creator) do |*args|
    if args.size >= argc
      call(*args)
    else
      send(creator) do |*more_args|
        args += more_args
        block.call(*args)
      end
    end
  end
end

def lambda?
  !!__is_lambda__
end