# A place has a number of tokens, and that's it.

PlaceState:Class
PlaceState_numTokens:AttributeLink (PlaceState -> Integer) {
  name = "numTokens";
  optional = False;
  constraint = `"numTokens cannot be negative" if get_value(get_target(this)) < 0 else None`;
}

of:Association (PlaceState -> Place) {
  # one-to-one
  source_lower_cardinality = 1;
  source_upper_cardinality = 1;
  target_lower_cardinality = 1;
  target_upper_cardinality = 1;
}