is_older, number_in_month done

sml/week1/date.sml

@@ -0,0 +1,32 @@
+(* year * month * day *)
+type Date = int * int * int
+
+fun fold f lst acc = 
+    case lst of
+        [] => acc
+        | head::tail => fold f tail (f head acc)
+
+fun is_older (
+    (y1, m1, d1): Date,
+    (y2, m2, d2): Date
+): bool =
+        let
+            val same_dates = y1 = y2 andalso m1 = m2 andalso d1 = d2
+            val older = y1 <= y2 andalso m1 <= m2 andalso d1 <= d2
+        in
+            if same_dates then false else older
+        end
+
+fun number_in_month (
+    dates: Date list,
+    month_to_find: int
+): int =
+    let         
+        fun count_month (_, month, _) occurences =  
+            if month = month_to_find
+            then occurences + 1
+            else occurences 
+    in
+        fold count_month dates 0
+    end
+

sml/week1/date_tests.sml

@@ -0,0 +1,57 @@
+use "test.sml";
+use "date.sml";
+
+
+val () = 
+    assert 
+        (is_older ((1999, 12, 31), (1999, 12, 31)) = false)
+        "is_older: same dates evaluates to false" 
+
+val () = 
+    assert 
+        (is_older ((2000, 11, 28), (2000, 11, 29)) = true)
+        "is_older: first date older than second by day" 
+
+val () = 
+    assert 
+        (is_older ((1999, 12, 31), (1999, 11, 31)) = false)
+        "is_older: first date greater by month" 
+
+val () = 
+    assert 
+        (is_older ((1999, 12, 31), (1999, 11, 31)) = false)
+        "is_older: first date greater by month" 
+
+val () = 
+    assert 
+        (is_older ((2000, 12, 31), (1999, 12, 31)) = false)
+        "is_older: first date greater by year" 
+
+val () = 
+    assert 
+        (number_in_month ([(2000, 12, 31)], 12) = 1)
+        "number_in_month: one date with exact month" 
+
+val () = 
+    let
+        val dates = [(2000, 12, 31), (2000, 12, 31)]
+        val month = 12
+        val expect = 2
+    in
+        assert 
+            (number_in_month (dates, month) = expect)
+            "number_in_month: two date with exact month"
+    end
+
+val () = 
+    let
+        val dates = []
+        val month = 12
+        val expect = 0
+    in
+        assert 
+            (number_in_month (dates, month) = expect)
+            "number_in_month: empty list"
+    end
+
+val () = complete ()

sml/week1/test.sml

@@ -0,0 +1,17 @@
+fun assert condition message = 
+    if condition 
+    then
+        print (message ^ "\n")
+    else 
+        let
+            val () = print ("Assert error: " ^ message ^ "\n")
+        in
+            OS.Process.exit OS.Process.failure
+        end
+
+fun complete () =
+    let
+        val () = print "All tests passed!"
+    in
+        OS.Process.exit OS.Process.success
+    end