Avatar of shmibs

shmibs's solution

to Raindrops in the OCaml Track

Published at Dec 08 2018 · 0 comments
Test suite

Convert a number to a string, the contents of which depend on the number's factors.

  • If the number has 3 as a factor, output 'Pling'.
  • If the number has 5 as a factor, output 'Plang'.
  • If the number has 7 as a factor, output 'Plong'.
  • If the number does not have 3, 5, or 7 as a factor, just pass the number's digits straight through.


  • 28's factors are 1, 2, 4, 7, 14, 28.
    • In raindrop-speak, this would be a simple "Plong".
  • 30's factors are 1, 2, 3, 5, 6, 10, 15, 30.
    • In raindrop-speak, this would be a "PlingPlang".
  • 34 has four factors: 1, 2, 17, and 34.
    • In raindrop-speak, this would be "34".

Getting Started

For installation and learning resources, refer to the exercism help page.


To work on the exercises, you will need Opam and Base. Consult opam website for instructions on how to install opam for your OS. Once opam is installed open a terminal window and run the following command to install base:

opam install base

To run the tests you will need OUnit. Install it using opam:

opam install ounit

Running Tests

A Makefile is provided with a default target to compile your solution and run the tests. At the command line, type:


Interactive Shell

utop is a command line program which allows you to run Ocaml code interactively. The easiest way to install it is via opam:

opam install utop

Consult utop for more detail.

Feedback, Issues, Pull Requests

The exercism/ocaml repository on GitHub is the home for all of the Ocaml exercises.

If you have feedback about an exercise, or want to help implementing a new one, head over there and create an issue. We'll do our best to help you!


A variation on a famous interview question intended to weed out potential candidates. http://jumpstartlab.com

Submitting Incomplete Solutions

It's possible to submit an incomplete solution so you can see how others have completed the exercise.


open OUnit2
open Raindrops

let ae exp got _test_ctxt = assert_equal ~printer:(fun x -> x) exp got

let tests = [
   "the sound for 1 is 1" >::
      ae "1" (raindrop 1);
   "the sound for 3 is Pling" >::
      ae "Pling" (raindrop 3);
   "the sound for 5 is Plang" >::
      ae "Plang" (raindrop 5);
   "the sound for 7 is Plong" >::
      ae "Plong" (raindrop 7);
   "the sound for 6 is Pling as it has a factor 3" >::
      ae "Pling" (raindrop 6);
   "2 to the power 3 does not make a raindrop sound as 3 is the exponent not the base" >::
      ae "8" (raindrop 8);
   "the sound for 9 is Pling as it has a factor 3" >::
      ae "Pling" (raindrop 9);
   "the sound for 10 is Plang as it has a factor 5" >::
      ae "Plang" (raindrop 10);
   "the sound for 14 is Plong as it has a factor of 7" >::
      ae "Plong" (raindrop 14);
   "the sound for 15 is PlingPlang as it has factors 3 and 5" >::
      ae "PlingPlang" (raindrop 15);
   "the sound for 21 is PlingPlong as it has factors 3 and 7" >::
      ae "PlingPlong" (raindrop 21);
   "the sound for 25 is Plang as it has a factor 5" >::
      ae "Plang" (raindrop 25);
   "the sound for 27 is Pling as it has a factor 3" >::
      ae "Pling" (raindrop 27);
   "the sound for 35 is PlangPlong as it has factors 5 and 7" >::
      ae "PlangPlong" (raindrop 35);
   "the sound for 49 is Plong as it has a factor 7" >::
      ae "Plong" (raindrop 49);
   "the sound for 52 is 52" >::
      ae "52" (raindrop 52);
   "the sound for 105 is PlingPlangPlong as it has factors 3, 5 and 7" >::
      ae "PlingPlangPlong" (raindrop 105);
   "the sound for 3125 is Plang as it has a factor 5" >::
      ae "Plang" (raindrop 3125);

let () =
  run_test_tt_main ("raindrops tests" >::: tests)
open Core

let wordmap = [3, "Pling"; 5, "Plang"; 7, "Plong"]

let raindrop (i : int) =
  |> List.map ~f:(fun (k, v) -> if Int.rem i k = 0 then v else "")
  |> String.concat
  |> fun s -> if s = "" then (Int.to_string i) else s

Community comments

Find this solution interesting? Ask the author a question to learn more.

What can you learn from this solution?

A huge amount can be learned from reading other people’s code. This is why we wanted to give exercism users the option of making their solutions public.

Here are some questions to help you reflect on this solution and learn the most from it.

  • What compromises have been made?
  • Are there new concepts here that you could read more about to improve your understanding?