static O mapLike rcurry(fO f, fO arg) {
  int n = numberOfFunctionArguments(f);
  if (n == 0) fail("function takes no arguments");
  if (n == 1) ret new F0 {
    O get() {
      ret callF(f, arg);
    }
  };
  if (n == 2)
    ret new F1 {
      O get(O a) {
        ret callF(f, a, arg);
      }
    };
  throw todo("currying a function with " + n + "arguments");
}

Began life as a copy of #1008681