# 4d47's solution

## to Leap in the Clojure Track

Published at Jul 13 2018 · 0 comments
Instructions
Test suite
Solution

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.

If your language provides a method in the standard library that does this look-up, pretend it doesn't exist and implement it yourself.

## Notes

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.

## Source

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

## Submitting Incomplete Solutions

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

### leap_test.clj

``````(ns leap-test
(:require [clojure.test :refer [deftest is]]
leap))

(deftest vanilla-leap-year
(is (leap/leap-year? 1996)))

(deftest any-old-year
(is (not (leap/leap-year? 1997))))

(deftest century
(is (not (leap/leap-year? 1900))))

(deftest exceptional-century
(is (leap/leap-year? 2400)))``````
``````(ns leap)

(defn leap-year? [y]
(let [divides (partial (comp zero? rem) y)]
(and (divides 4)
(or (not (divides 100)) (divides 400)))))``````