CS61A: The Structure and Interpretation of Computer Programs(inst.eecs.berkeley.edu)

    (defn pi
      ([] (float (* 4 (pi 1 0.01 0 true))))
      ([term tol accum pn]
        (let
          [t (/ 1 term)
           a ((if pn + -) accum t)]
          (if (< (* 4 t) tol)
            a
            (pi (+ term 2) tol a (not pn))
          )
        )
      )
    )

    if (type == enum.FOO) {
      UnaryOperator<String> trim = s -> s.replaceFirst("^0+", "");
      idFun = trim.compose(DTO::getFooNum);
    } else {
      idFun = DTO::getBarNum;
    }

    // ...

    Set<String> ids = results.stream().map(idFun).collect(Collectors.toSet());

    @sorted = map  { $_->[0] }
          sort { $a->[1] <=> $b->[1]}
          map  { [$_, -s $_] }    # get the size of the file on disk
          @files;