Module:Age
Documentation for this module may be created at Module:Age/doc
--[[ Code for some date functions, including implementations of:
{{Age in days}} age_days
{{Age in years and months}} age_ym
{{Gregorian serial date}} gsd_ymd
Calendar functions will be needed in many areas, so this may be superseded
by some other system, perhaps using PHP functions accessed via mediawiki.
]]
local MINUS = '−' -- Unicode U+2212 MINUS SIGN
local function number_name(number, singular, plural, sep)
-- Return the given number, converted to a string, with the
-- separator (default space) and singular or plural name appended.
plural = plural or (singular .. 's')
sep = sep or ' '
return tostring(number) .. sep .. ((number == 1) and singular or plural)
-- this uses an interesting trick of Lua:
-- * and returns false if the first argument is false, and the second otherwise, so (number==1) and singular returns singular if its 1, returns false if it is only 1
-- * or returns the first argument if it is not false, and the second argument if the first is false
-- * so, if number is 1, and evaluates (true and singular) returning (singular); or evaluates (singular or plural), finds singular non-false, and returns singular
-- * but, if number is not 1, and evaluates (false and singular) returning (false); or evaluates (false or plural), and is forced to return plural
end
local function strip_to_nil(text)
-- If text is a non-blank string, return its content with no leading
-- or trailing whitespace.
-- Otherwise return nil (a nil or empty string argument gives a nil
-- result, as does a string argument of only whitespace).
if type(text) == 'string' then
local result = text:match("^%s*(.-)%s*$")
if result ~= '' then
return result
end
end
return nil
end
local function is_leap_year(year)
-- Return true if year is a leap year, assuming Gregorian calendar.
return year % 4 == 0 and (year % 100 ~= 0 or year % 400 == 0)
end
local function days_in_month(year, month)
-- Return number of days (1..31) in given month (1..12).
local month_days = { 31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31 }
if month == 2 and is_leap_year(year) then
return 29
end
return month_days[month]
end
-- A table to get current year/month/day (UTC), but only if needed.
local current = setmetatable({}, {
__index = function (self, key)
local d = os.date('!*t')
self.year = d.year
self.month = d.month
self.day = d.day
return rawget(self, key)
end
})
local function date_component(named, positional, component)
-- Return the first of the two arguments that is not nil and is not empty.
-- If both are nil, return the current date component, if specified.
-- The returned value is nil or is a number.
-- This translates empty arguments passed to the template to nil, and
-- optionally replaces a nil argument with a value from the current date.
named = strip_to_nil(named)
if named then
return tonumber(named)
end
positional = strip_to_nil(positional)
if positional then
return tonumber(positional)
end
if component then
return current[component]
end
return nil
end
local function gsd(year, month, day)
-- Return the Gregorian serial day (an integer >= 1) for the given date,
-- or return nil if the date is invalid (only check that year >= 1).
-- This is the number of days from the start of 1 AD (there is no year 0).
-- This code implements the logic in [[Template:Gregorian serial date]].
if year < 1 then
return nil
end
local floor = math.floor
local days_this_year = (month - 1) * 30.5 + day
if month > 2 then
if is_leap_year(year) then
days_this_year = days_this_year - 1
else
days_this_year = days_this_year - 2
end
if month > 8 then
days_this_year = days_this_year + 0.9
end
end
days_this_year = floor(days_this_year + 0.5)
year = year - 1
local days_from_past_years = year * 365
+ floor(year / 4)
- floor(year / 100)
+ floor(year / 400)
return days_from_past_years + days_this_year
end
local Date = {
-- A naive date that assumes the Gregorian calendar always applied.
year = 0, -- 1 to 9999 (0 if never set)
month = 1, -- 1 to 12
day = 1, -- 1 to 31
isvalid = false,
new = function (self, o)
o = o or {}
setmetatable(o, self)
self.__index = self
return o
end
}
function Date:__lt(rhs)
-- Return true if self < rhs.
if self.year < rhs.year then
return true
elseif self.year == rhs.year then
if self.month < rhs.month then
return true
elseif self.month == rhs.month then
return self.day < rhs.day
end
end
return false
-- probably simplify to return (self.year < rhs.year) or ((self.year == rhs.year) and ((self.month < rhs.month) or ((self.month == rhs.month) and (self.day < rhs.day))))
-- would be just as efficient, as lua does not evaluate second argument of (true or second_argument)
-- or similarly return self.year < rhs.year ? true : self.year > rhs.year ? false : self.month < rhs.month ? true : self.month > rhs.month ? false : self.day < rhs.day
end
function Date:set_current()
-- Set date from current time (UTC) and return self.
self.year = current.year
self.month = current.month
self.day = current.day
self.isvalid = true
return self
end
function Date:set_ymd(y, m, d)
-- Set date from year, month, day (strings or numbers) and return self.
-- LATER: If m is a name like "March" or "mar", translate it to a month.
y = tonumber(y)
m = tonumber(m)
d = tonumber(d)
if type(y) == 'number' and type(m) == 'number' and type(d) == 'number' then
self.year = y
self.month = m
self.day = d
self.isvalid = (1 <= y and y <= 9999 and 1 <= m and m <= 12 and
1 <= d and d <= days_in_month(y, m))
end
return self
end
local DateDiff = {
-- Simple difference between two dates, assuming Gregorian calendar.
isnegative = false, -- true if second date is before first
years = 0,
months = 0,
days = 0,
new = function (self, o)
o = o or {}
setmetatable(o, self)
self.__index = self
return o
end
}
function DateDiff:set(date1, date2)
-- Set difference between the two dates, and return self.
-- Difference is negative if the second date is older than the first.
local isnegative
if date2 < date1 then
isnegative = true
date1, date2 = date2, date1
else
isnegative = false
end
-- It is known that date1 <= date2.
local y1, m1, d1 = date1.year, date1.month, date1.day
local y2, m2, d2 = date2.year, date2.month, date2.day
local years, months, days = y2 - y1, m2 - m1, d2 - d1
if days < 0 then
days = days + days_in_month(y1, m1)
months = months - 1
end
if months < 0 then
months = months + 12
years = years - 1
end
self.years, self.months, self.days, self.isnegative = years, months, days, isnegative
return self
end
function DateDiff:age_ym()
-- Return text specifying difference in years, months.
local sign = self.isnegative and MINUS or ''
local mtext = number_name(self.months, 'month')
local result
if self.years > 0 then
local ytext = number_name(self.years, 'year')
if self.months == 0 then
result = ytext
else
result = ytext .. ', ' .. mtext
end
else
if self.months == 0 then
sign = ''
end
result = mtext
end
return sign .. result
end
local function error_wikitext(text)
-- Return message for display when template parameters are invalid.
local prefix = '[[Module talk:Age|Module error]]:'
local cat = '[[Category:Age error]]'
return '<span style="color:black; background-color:pink;">' ..
prefix .. ' ' .. text .. cat .. '</span>'
end
local function age_days(frame)
-- Return age in days between two given dates, or
-- between given date and current date.
-- This code implements the logic in [[Template:Age in days]].
-- Like {{Age in days}}, a missing argument is replaced from the current
-- date, so can get a bizarre mixture of specified/current y/m/d.
local args = frame:getParent().args
local year1 = date_component(args.year1 , args[1], 'year' )
local month1 = date_component(args.month1, args[2], 'month')
local day1 = date_component(args.day1 , args[3], 'day' )
local year2 = date_component(args.year2 , args[4], 'year' )
local month2 = date_component(args.month2, args[5], 'month')
local day2 = date_component(args.day2 , args[6], 'day' )
local gsd1 = gsd(year1, month1, day1)
local gsd2 = gsd(year2, month2, day2)
if gsd1 and gsd2 then
local sign = ''
local result = gsd2 - gsd1
if result < 0 then
sign = MINUS
result = -result
end
return sign .. tostring(result)
end
return error_wikitext('Cannot handle dates before the year 1 AD')
end
local function age_ym(frame)
-- Return age in years and months between two given dates, or
-- between given date and current date.
local args = frame:getParent().args
local fields = {}
for i = 1, 6 do
fields[i] = strip_to_nil(args[i])
end
local date1, date2
if fields[1] and fields[2] and fields[3] then
date1 = Date:new():set_ymd(fields[1], fields[2], fields[3])
end
if not (date1 and date1.isvalid) then
return error_wikitext('Need date: year, month, day')
end
if fields[4] and fields[5] and fields[6] then
date2 = Date:new():set_ymd(fields[4], fields[5], fields[6])
if not date2.isvalid then
return error_wikitext('Second date should be year, month, day')
end
else
date2 = Date:new():set_current()
end
return DateDiff:new():set(date1, date2):age_ym()
end
local function gsd_ymd(frame)
-- Return Gregorian serial day of the given date, or the current date.
-- Like {{Gregorian serial date}}, a missing argument is replaced from the
-- current date, so can get a bizarre mixture of specified/current y/m/d.
-- This accepts positional arguments, although the original template does not.
local args = frame:getParent().args
local year = date_component(args.year , args[1], 'year' )
local month = date_component(args.month, args[2], 'month')
local day = date_component(args.day , args[3], 'day' )
local result = gsd(year, month, day)
if result then
return tostring(result)
end
return error_wikitext('Cannot handle dates before the year 1 AD')
end
return { age_days = age_days, age_ym = age_ym, gsd = gsd_ymd }