ðŸŽ‰ Exercism Research is now launched. Help Exercism, help science and have some fun at research.exercism.io ðŸŽ‰

# craigmaloney's solution

## to Leap in the Scheme Track

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

#### Note:

This solution was written on an old version of Exercism. The tests below might not correspond to the solution code, and the exercise may have changed since this code was written.

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.scm

``````;; Load SRFI-64 lightweight testing specification
(use-modules (srfi srfi-64))

;; Suppress log file output. To write logs, comment out the following line:
(module-define! (resolve-module '(srfi srfi-64)) 'test-log-to-file #f)

;; Require module
(use-modules (leap-year))

(test-begin "leap-year")

(test-eqv "vanilla-leap-year"
#t
(leap-year? 1996))

(test-eqv "any-old-year"
#f
(leap-year? 1997))

(test-eqv "non-leap-even-year"
#f
(leap-year? 1998))

(test-eqv "century"
#f
(leap-year? 1900))

(test-eqv "exceptional-century"
#t
(leap-year? 2400))

(test-end "leap-year")``````
``````(define-module (leap-year)
#:export (leap-year?))

(define leap-year?
(lambda (year)
(cond
[(not (zero? (remainder year 4))) #f]
[(not (zero? (remainder year 100))) #t]
[(not (zero? (remainder year 400))) #f]
[#t]
)
)
)``````