static int copyConceptFields(Concept a, Concept b) {
  int changes = 0;
  for (S field : conceptFields(a))
    changes += cset(b, field, cget(a, field));
  ret changes;
}

static int copyConceptFields(Concept a, Concept b, S... fields) {
  int changes = 0;
  for (S field : fields)
    changes += cset(b, field, cget(a, field));
  ret changes;
}