static L<Int> ai_matchPattern_splitIndices(S pat, S input) {
  pat = quoteUnlessQuoted(pat);
  S function = ai_forward(pat, "can be matched with");
  function = function + "_splitIndices";
  if (!has_verified(function, "is", "a safe function to call")) fail("no mama: " + function);
  ret (L<Int>) callAndMake(function, unquote(pat), input);
}