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

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