assignment_01.txt

val months = [Date.Jan,Date.Feb,Date.Mar,Date.Apr,Date.May,Date.Jun,Date.Jul,Date.Aug,Date.Sep,Date.Oct,Date.Nov,Date.Dec];
fun make_date(month:int,day:int,year:int) =
  let
    val new_date = {day=day,hour=19,minute=27,month=List.nth(months,month-1),offset=NONE,second=23,year=year};
   in
       Date.date new_date
   end
(*

   Using the library $SMLNJ-BASIS/basis.cm that comes with the SMLNJ .
   This library already has Date and Time functions build in.
*)


(* 1 val is_older = fn : (int * int * int) * (int * int * int) -> bool *)

fun is_older(date1 : (int * int * int), date2: (int * int * int)) =
    let
      val d1 = make_date(#1 date1,#2 date1, #3 date1);
      val d2 = make_date(#1 date2,#2 date2, #3 date2);
    in
      if Date.compare(d1,d2) = LESS
      then true
      else false
    end

(* 2 val number_in_month = fn : (int * int * int) list * int -> int *)

fun number_in_month(dates : (int * int * int) list, nmonth : int) =
	let fun month_check( date : (int * int * int)) =
	   if Date.month((make_date date)) = List.nth(months,nmonth-1)
	   then 1
	   else 0
	in
		if null dates
   		then 0
   		else month_check(hd dates) + number_in_month( tl dates, nmonth)
	end

(* 3 val number_in_months = fn : (int * int * int) list * int list -> int *)

fun number_in_months(dates : (int * int * int) list, nmonths : int list) =
         if null dates orelse null nmonths
         then 0
         else number_in_month(dates , hd nmonths) + number_in_months(dates , tl nmonths )

 (* 4 val dates_in_month = fn : (int * int * int) list * int -> (int * int * int) list *)

 fun dates_in_month(dates : (int * int * int) list, nmonth : int) =
 	let fun month_check( date : (int * int * int)) =
	   if Date.month((make_date date)) = List.nth(months,nmonth-1)
	   then [date]
	   else []
	in
		if null dates
   		then []
   		else month_check(hd dates) @ dates_in_month( tl dates, nmonth)
	end


(* 5 val dates_in_months = fn : (int * int * int) list * int list -> (int * int * int) list *)

fun dates_in_months(dates : (int * int * int) list, nmonths : int list) =
         if null dates orelse null nmonths
         then []
         else dates_in_month(dates , hd nmonths) @ dates_in_months(dates , tl nmonths )

(* 6 val get_nth = fn : string list * int -> string *)

fun get_nth(strings : string list, n : int) =
  let fun count_up_to(shorter_strings : string list,i : int) =
    if i = n
    then hd shorter_strings
    else count_up_to(tl shorter_strings,i + 1)
  in
     if null strings
     then hd strings
     else count_up_to(strings,1)
  end
fun get_nth2(strings : string list, n : int) =
   List.nth(strings, n-1 )

(* 7 val = date_to_string = fn : int * int * int -> string *)

fun date_to_string(date : (int * int * int)) =
   let

    val nmonth = #1 date;
    val day    = #2 date;
    val year   = #3 date;

    val month=List.nth(months,nmonth -1 );

    val a_date = Date.date {day=day,hour=19,minute=27,month=month,offset=NONE,second=23,year=year};

    in
      Date.fmt "%B %d, %Y" a_date
    end

(* 8 val number_before_reaching_sum = fn : int * int list -> int *)

fun number_before_reaching_sum(n : int , ns : int list) =
    let
      fun sum_up_to(n : int ,ns : int list) =
        if (n - hd(ns)) <= 0
        then 0
        else hd(ns) + sum_up_to( n - hd(ns), tl(ns))
    in
      sum_up_to(n,ns)

    end


(* 9 val what_month = fn : int -> int *)
(* 10 val month_range = fn : int * int -> int list *)
(* 11 val oldest = fn : (int * int * int) list -> (int * int * int) option *)