Last Friday of each month

Last Friday of each month is a draft programming task. It is not yet considered ready to be promoted as a complete task, for reasons that should be found in its talk page.

Write a program or a script that returns the last Fridays of each months of a given year provided as argument on the command line.

Example of an expected output:

./last_fridays 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

OCaml

<lang ocaml>#load "unix.cma" open Unix

let usage() =

 Printf.eprintf "%s <year>\n" Sys.argv.(0);
 exit 1

let print_date t =

 Printf.printf "%d-%02d-%02d\n" (t.tm_year + 1900) (t.tm_mon + 1) t.tm_mday

let is_date_ok tm t =

 (tm.tm_year = t.tm_year &&
  tm.tm_mon  = t.tm_mon  &&
  tm.tm_mday = t.tm_mday)

let () =

 let _year =
   try int_of_string Sys.argv.(1)
   with _ -> usage()
 in
 let year = _year - 1900 in
 let fridays = Array.make 12 (Unix.gmtime 0.0) in
 for month = 0 to 11 do
   for day_of_month = 1 to 31 do
     let tm = { (Unix.gmtime 0.0) with 
       tm_year = year;
       tm_mon = month;
       tm_mday = day_of_month;
     } in
     let _, t = Unix.mktime tm in
     if is_date_ok tm t  (* check for months that have less than 31 days *)
     && t.tm_wday = 5  (* is a friday *)
     then fridays.(month) <- t
   done;
 done;
 Array.iter print_date fridays</lang>

Output:

$ ocaml last_fridays.ml 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

Pike

<lang Pike>int(0..1) last_friday(object day) {

  return day->week_day() == 5 && 
         day->month_day() > day->month()->number_of_days()-7; 

}

void main() {

   array days = filter(Calendar.Year(2012)->months()->days()[*], last_friday);
   write("%{%s\n%}\n", days->format_ymd());

}</lang>