static S ctxCallFunction(S fname, L<S> args) {
  if (eqic(fname, "tolowercase"))
    ret toLower(first(args));
  if (eqic(fname, "length"))
    ret lstr(first(args));
  if (eqic(fname, "firstupper"))
    ret firstToUpper(first(args));
  throw todo("ctx function " + fname);
}