Bug in rights() for join

[neilconway]

Test case:

require "rubygems"
require "bud"

class JoinTest
  include Bud

  state do
    channel :msg_recv, [:@loc, :recv_id]
    scratch :deliver_msg, msg_recv.schema
    table :recv_done_max, [] => [:recv_id]
  end

  bootstrap do
    recv_done_max <= [[-1]]
    msg_recv <~ [[ip_port, 0]]
  end

  bloom do
    deliver_msg <= (msg_recv * recv_done_max).pairs do |b, m|
      b if b.recv_id == (m.recv_id + 1)
    end
    recv_done_max <+ (deliver_msg * recv_done_max).rights {|k| puts "k = #{k.inspect}, k.recv_id = #{k.recv_id}"; [k.recv_id + 1]}
#    recv_done_max <+ (deliver_msg * recv_done_max).pairs {|x, k| puts "k = #{k.inspect}, k.recv_id = #{k.recv_id}"; [k.recv_id + 1]}                                                                       
  end
end

j = JoinTest.new
j.run_fg

Running the test case yields:

k = [-1], k.recv_id = 
Exception handling network message (channel 'msg_recv'): Exception during Bud evaluation.
Exception: #<NoMethodError: undefined method `+' for nil:NilClass>.
Rule: recv_done_max < (+(deliver_msg * recv_done_max).rights do |k|
  puts("k = #{k.inspect}, k.recv_id = #{k.recv_id}")
  [(k.recv_id + 1)]
end)

If you replace the call to rights() with pairs() (see the commented-out alternative), you instead get the expected output (and no error):

k = [-1], k.recv_id = -1