[
  {"op": "source", "role": "price", "kind": "F64"},
  {"op": "add", "type": "Sub", "name": "a"},
  {"op": "add", "type": "Sub", "name": "b"},
  {"op": "feed", "role": "price", "into": ["a.lhs", "b.rhs"]},
  {"op": "connect", "from": "a.value", "to": "b.lhs"},
  {"op": "connect", "from": "b.value", "to": "a.rhs"},
  {"op": "expose", "from": "a.value", "as": "out"}
]