static File transpiledStandardFunctions_file(TreeSet<S> functionSet) {
  S name = uniqueFileNameUsingMD5_80_v2(join("+", functionSet));
  File dir = javaxCachesDir("Transpiled Standard Functions");
  saveTextFileUnlessExists(newFile(dir, name + ".functions"), lines(functionSet));
  ret newFile(dir, name + ".java");
}