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Stored size: 1.28 KB
Contents
#lang racket
(require racket/date)
(define (leap-year? year)
(or (and (zero? (modulo year 4))
(not (zero? (modulo year 100))))
(zero? (modulo year 400))))
(define (days-in-month year month)
(case month
[(1 3 5 7 8 10 12) 31]
[(4 6 9 11) 30]
[(2) (if (leap-year? year) 29 28)]))
(define (make-date year month day)
(seconds->date (find-seconds 0 0 0 day month year #f) #f))
(define (meetup-day year month weekday week)
(let ([first-of-week
(case week
[(first) 1]
[(second) 8]
[(teenth) 13]
[(third) 15]
[(fourth) 22]
[(last) (- (days-in-month year month) 6)]
[else (raise-argument-error 'meetup-day "week" 3 year month weekday week)])]
[weekday
(case weekday
[(Sunday) 0]
[(Monday) 1]
[(Tuesday) 2]
[(Wednesday) 3]
[(Thursday) 4]
[(Friday) 5]
[(Saturday) 6]
[else (raise-argument-error 'meetup-day "weekday" 3 year month weekday week)])])
(make-date year month
(+ first-of-week
(modulo
(- weekday
(date-week-day (make-date year month first-of-week))) 7)))))
(provide meetup-day)
Version data entries
130 entries across 130 versions & 1 rubygems