Programming Languages Programming Assignment 1

fun is_older (date1 : int*int*int, date2 : int*int*int)=
   let 
      fun toNumber (date : int*int*int) = (#1 date)*10000 +  (#2 date)*100 +  (#3 date)      
   in
       if (toNumber(date1) <  toNumber(date2)) then true else false
   end
fun number_in_month (datelist : (int*int*int) list, month : int) = 
   let fun isMonth (date : int*int*int) = if ((#2 date) = month) then 1 else 0
   in
      if null datelist
      then 0
      else isMonth(hd(datelist)) + number_in_month(tl datelist, month)
   end

fun number_in_months (datelist : (int*int*int) list, months : int list) = 
   let 
      fun isMonths (date : int*int*int, months : int list) = 
         let fun isMonth (date : int*int*int, month : int) = if ((#2 date) = month) then 1 else 0
         in
            if null months
            then 0
            else isMonth(date, hd(months)) + isMonths(date, tl months)
         end
   in
         if null datelist
         then 0
         else isMonths(hd(datelist), months) + number_in_months(tl datelist, months)
   end

fun dates_in_month (datelist : (int*int*int) list, month : int) = 
   let 
      fun isDateInMonth (date : int*int*int) =  if ((#2 date) = month) then [date] else []
   in
      if null datelist
      then []
      else isDateInMonth(hd(datelist)) @ dates_in_month(tl datelist, month)
   end
fun dates_in_months (datelist : (int*int*int) list, months : int list) = 
   let 
      fun isDatesInMonths (date : int*int*int, months : int list) =
         let 
            fun isDateInMonth (date : int*int*int, month : int) =  if ((#2 date) = month) then [date] else []
         in 
           if null months
           then []
           else isDateInMonth(date, hd(months)) @ isDatesInMonths(date, tl months)
         end
   in
      if null datelist
      then []
      else isDatesInMonths(hd(datelist), months) @ dates_in_months(tl datelist, months)
   end
fun get_nth (stringlist : string list, n : int) = 
   if (n = 1)
   then hd(stringlist)
   else get_nth(tl stringlist, n - 1);
fun date_to_string (date : int*int*int) =
   let val MonthList = ["January", "February", "March", "April", "May", "June", "July", "August", "September", "October", "November", "December"];
   in
      get_nth(MonthList, #2 date) ^ " " ^ Int.toString(#3 date) ^ ", " ^ Int.toString(#1 date)
   end
fun number_before_reaching_sum (sum : int, datalist : int list) = 
   if (sum <= hd (datalist))
   then 0
   else 1 + number_before_reaching_sum (sum - hd (datalist), tl datalist);

fun what_month (day : int) =
   let val daysInMonthList = [31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31]
   in
     number_before_reaching_sum (day, daysInMonthList) + 1
   end
fun month_range (day1 : int, day2 : int) =
   if (day1 > day2)
   then []
   else [what_month(day1)] @ month_range(day1 + 1, day2);
fun oldest (datelist : (int*int*int) list) = 
   if null datelist
   then NONE
   else 
      let 
          fun oldest_nonempty (xs : (int*int*int) list ) =
              if null (tl xs)
              then hd xs
              else let val tl_ans = oldest_nonempty(tl xs)
                   in 
                        if is_older(hd xs,  tl_ans)
                        then hd xs
                        else tl_ans
                   end
      in
         SOME(oldest_nonempty datelist)
      end	
fun unique (months : int list)	= 
   let 
      fun loop (result : int list, months : int list) = 
	     if null months
         then result
		 else 
		    let 
               fun contains (result : int list, month : int) = 
			      if null result
				  then false
				  else if (hd result = month)
				     then true
                     else contains(tl result, month) 
            in
		       if (contains (result,(hd months)))
		       then loop(result, tl months)
			   else loop((hd months) :: result,  tl months)
            end			   
   in
      loop([], months)
   end
fun number_in_months_challenge (datelist : (int*int*int) list, months : int list) = number_in_months (datelist, unique(months))
fun dates_in_months_challenge (datelist : (int*int*int) list, months : int list) = dates_in_months (datelist, unique(months))
   

Test Code:

val is_older_Test = is_older((1997, 1, 11), (1997, 2, 1));
val number_in_month_test = number_in_month([(1997, 5, 11), (1999, 6, 11), (1991, 5, 21), (1992, 7, 11), (1993, 5, 11), (1991, 11, 11), (1997, 1, 1), (1992, 5, 13), (1998, 9, 30)], 5);
val number_in_months_test = number_in_months([(1997, 5, 11), (1999, 6, 11), (1991, 5, 21), (1992, 7, 11), (1993, 5, 11), (1991, 11, 11), (1997, 1, 1), (1992, 5, 13), (1998, 9, 30)], [5, 6]);
val dates_in_month_test = dates_in_month([(1997, 5, 11), (1999, 6, 11), (1991, 5, 21), (1992, 7, 11), (1993, 5, 11), (1991, 11, 11), (1997, 1, 1), (1992, 5, 13), (1998, 9, 30)], 5);
val dates_in_months_test = dates_in_months([(1997, 5, 11), (1999, 6, 11), (1991, 5, 21), (1992, 7, 11), (1993, 5, 11), (1991, 11, 11), (1997, 1, 1), (1992, 5, 13), (1998, 9, 30)], [5, 6]);
val get_nth_test = get_nth(["January", "February", "March", "April", "May", "June", "July", "August", "September", "October", "November", "December"] , 4);
val date_to_string_test = date_to_string((2013, 1, 20));
val number_before_reaching_sum_test = number_before_reaching_sum (100, [31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31]);
val what_month_test = what_month(32);
val month_range_test = month_range(28, 33);
val oldest_test = oldest([(1997, 5, 11), (1999, 6, 11), (1991, 5, 21), (1992, 7, 11), (1993, 5, 11), (1991, 11, 11), (1997, 1, 1), (1992, 5, 13), (1998, 9, 30)]);
val oldest_test1 = oldest [];
val number_before_reaching_sum_test = number_before_reaching_sum (1, [2]);
val number_before_reaching_sum_test = number_before_reaching_sum (5, [3,1,2]);
val number_before_reaching_sum_test = number_before_reaching_sum (5, [3,2,2]);
val number_before_reaching_sum_test = number_before_reaching_sum (4, [1,4,1,1]);
val number_before_reaching_sum_test = number_before_reaching_sum (6, [4,1,1,1]);
val number_before_reaching_sum_test = number_before_reaching_sum (10, [1,2,3,4,5]);