macros wr and rd:

  wr(out, 7)

  ->

  meet(out)
  c(out) = 7
  part(out)


  a = rd(in)

  ->

  pass(in)
  a = c(in)


Could be the other way:

  WR(out, 7)

  ->

  c(out) = 7
  pass(out)


  a = RD(in)

  ->

  meet(in)
  a = c(in)
  part(in)


Lets do both, use capitalisation (or append a number?)
to indicate which pair we're using.