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Contents
(defmodule meetup
(doc "Calculating the date of meetups.")
(export (schedule 4)))
(defun WEEKDAY-MAP ()
"Days of the week enumerator."
(map 'monday 1
'tuesday 2
'wednesday 3
'thursday 4
'friday 5
'saturday 6
'sunday 7))
(defun SCHEDULE-MAP ()
"Enumerator for specifying an occurrence of a weekday in a month."
(map 'first 0
'second 1
'third 2
'fourth 3
'teenth 4
'last 5))
(defun weekday-num (weekday)
(maps:get weekday (WEEKDAY-MAP)))
(defun schedule-num (schedule)
(maps:get schedule (SCHEDULE-MAP)))
(defun schedule
"Given a year, month, and weekday and schedule atoms, return the specified date."
([year month weekday 'last]
(let ((last-day (calendar:last_day_of_the_month year month)))
(date-in-week weekday `#(,year ,month ,(- last-day 6)))))
([year month weekday 'teenth]
(date-in-week weekday `#(,year ,month 13)))
([year month weekday nth]
(let ((start-day (+ 1 (* 7 (schedule-num nth)))))
(date-in-week weekday `#(,year ,month ,start-day)))))
(defun date-in-week
([weekday (= `#(,_ ,_ ,day) start-date)]
(date-in-range (weekday-num weekday) start-date (+ day 6))))
(defun date-in-range
([day-num (= `#(,year ,month ,day) date) end-day] (when (=< day end-day))
(if (=:= day-num (calendar:day_of_the_week date))
date
(date-in-range day-num `#(,year ,month ,(+ day 1)) end-day))))
Version data entries
396 entries across 396 versions & 1 rubygems