funclang series2: Added error messages to exceptions.

funclang-taddeus/series2/ass5.ml

@@ -17,7 +17,7 @@ test_isLeapYear 1904 true;;
 (* Give a proper English character string representation of a date *)
 let date2str day month year =
     if day < 1 || day > 31 || month < 1 || month > 12 || year < 0 then
-        raise Exit
+        raise (Failure "invalid date")
     else
         (* Get the textual postfix of a day number *)
         let getDayPostfix day =
@@ -45,7 +45,7 @@ test_date2str 9 2 2010 "February 9th, 2010";;
 
 (* Sum all digits of a natural number *)
 let rec sum_digits n =
-    if n < 0 then raise Exit else
+    if n < 0 then raise (Failure "cannot sum digits in integers below 0") else
     let str = string_of_int n in
     let l = String.length str in
     if l = 1 then