svoid assertDoublesVeryClose_warnOnly(S msg default "", double x, double y, double threshold) {
  if (abs(x-y) > threshold)
    warn(msg, x, y);
}

svoid assertDoublesVeryClose(IF0<S> msg, double x, double y, double threshold) {
  if (abs(x-y) > threshold)
    warn(callF(msg, x, y));
}