🎉 Exercism Research is now launched. Help Exercism, help science and have some fun at research.exercism.io 🎉
Avatar of SeedyROM

SeedyROM's solution

to Leap in the OCaml Track

Published at Mar 08 2021 · 0 comments
Test suite

Given a year, report if it is a leap year.

The tricky thing here is that a leap year in the Gregorian calendar occurs:

on every year that is evenly divisible by 4
  except every year that is evenly divisible by 100
    unless the year is also evenly divisible by 400

For example, 1997 is not a leap year, but 1996 is. 1900 is not a leap year, but 2000 is.


Though our exercise adopts some very simple rules, there is more to learn!

For a delightful, four minute explanation of the whole leap year phenomenon, go watch this youtube video.

Getting Started

  1. Install the Exercism CLI.

  2. Install OCaml.

  3. For library documentation, follow Useful OCaml resources.

Running Tests

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


Submitting Incomplete Solutions

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

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 or submit a PR. We welcome new contributors!


JavaRanch Cattle Drive, exercise 3 http://www.javaranch.com/leap.jsp


(* leap - 1.5.1 *)
open OUnit2
open Leap

let ae exp got _test_ctxt = assert_equal exp got ~printer:string_of_bool

let tests = [
  "year not divisible by 4 in common year" >::
  ae false (leap_year 2015);
  "year divisible by 2, not divisible by 4 in common year" >::
  ae false (leap_year 1970);
  "year divisible by 4, not divisible by 100 in leap year" >::
  ae true (leap_year 1996);
  "year divisible by 100, not divisible by 400 in common year" >::
  ae false (leap_year 2100);
  "year divisible by 400 in leap year" >::
  ae true (leap_year 2000);
  "year divisible by 200, not divisible by 400 in common year" >::
  ae false (leap_year 1800);

let () =
  run_test_tt_main ("leap tests" >::: tests)
let leap_year year = 
    let divisible_by_4   = year mod 4   == 0
    and divisible_by_100 = year mod 100 == 0
    and divisible_by_400 = year mod 400 == 0 in 
    match divisible_by_4 with
    | false -> false
    | true  ->
    match divisible_by_100 with
    | false -> true
    | true  -> divisible_by_400

Community comments

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

SeedyROM's Reflection

This is my incredibly verbose interpretation of the leap year method, using match fallthroughs. All of my let's more than likely get optimized away and the branch path is the same as less descriptive implementation.