add comments and tests

lab03/part1.ml

@@ -1,3 +1,5 @@
+(** [digits n] takes a positive integer [n] and returns
+    a list of integers of each digit in the number [n] *)
 let digits n =
   let rec digits' n acc =
     if n = 0 then acc
@@ -5,5 +7,30 @@ let digits n =
   in
   digits' n [];;
 
+(**/**)
+let test_digits () =
+  assert (digits 0 = []);
+  assert (digits 123 = [1;2;3]);
+  assert (digits 123040 = [1;2;3;0;4;0])
+(**/**)
+
+(** [int_of_digits d] takes a list of positive integers [d]
+    and returns a single number where each digit is from the
+    list [d]
+  *)
 let int_of_digits d =
   (List.fold_left (fun x acc -> (x + acc) * 10) 0 d) / 10;;
+
+(**/**)
+let test_int_of_digits () =
+  assert (int_of_digits [] = 0);
+  assert (int_of_digits [0] = 0);
+  assert (int_of_digits [0;0;1;2;3] = 123);
+  assert (int_of_digits [2;0;0;5] = 2005)
+(**/**)
+
+(**/**)
+let run_all_tests () =
+  test_digits();
+  test_int_of_digits()
+(**/**)