Last Friday of each month: Difference between revisions

=={{header|Erlang}}==

<lang Erlang>

-module( last_date_each_month ).

-export( [monday/1, tuesday/1, wednesday/1, thursday/1, friday/1, saturday/1, sunday/1] ).

monday( Year ) -> last( Year, 1 ).

tuesday( Year ) -> last( Year, 2 ).

wednesday( Year ) -> last( Year, 3 ).

thursday( Year ) -> last( Year, 4 ).

friday( Year ) -> last( Year, 5 ).

saturday( Year ) -> last( Year, 6 ).

sunday( Year ) -> last( Year, 7 ).

last( Year, Week_day ) ->

Months = lists:seq( 1, 12 ),

Months_days = [{X, Y} || X <- Months, Y <- lists:seq(calendar:last_day_of_the_month(Year, X), calendar:last_day_of_the_month(Year, X) - 7, -1), calendar:valid_date(Year, X, Y), calendar:day_of_the_week(Year, X, Y) =:= Week_day],

[{Year, X, proplists:get_value(X, Months_days)} || X <- Months].

</lang>

{{out}}

<pre>

32> [io:fwrite("~B-~2.10.0B-~B~n", [Y,M,D]) || {Y,M,D} <- last_date_each_month:friday(2012)].

2012-01-27

2012-02-24

2012-03-30

2012-04-27

2012-05-25

2012-06-29

2012-07-27

2012-08-31

2012-09-28

2012-10-26

2012-11-30

2012-12-28

</pre>