Solve day 2 in SML

day_2.sml

@@ -0,0 +1,59 @@
+val file = TextIO.openIn "day_2.txt";
+val input = TextIO.inputAll file;
+TextIO.closeIn file;
+
+fun equals a b = a = b
+fun non f x = not (f x)
+
+val maxRed = 12
+val maxGreen = 13
+val maxBlue = 14
+
+val possibleGames =
+  let val lines = String.tokens (equals #"\n") input
+  in
+    List.filter
+      (fn line =>
+        let
+          val game = List.last (String.tokens (equals #":") line)
+          val rounds = String.tokens (equals #";") game
+          val rounds = map
+            (fn round => String.extract (round, 1, NONE))
+            rounds
+        in
+          List.all
+            (fn round =>
+              let
+                val reveals = String.tokens (non Char.isAlphaNum) round
+                val revealPairs = ListPair.zip (
+                  (List.filter (fn elem => (Int.fromString elem) = NONE) reveals),
+                  (List.mapPartial Int.fromString reveals)
+                )
+              in
+                List.all
+                  (fn revealPair =>
+                    (#2 revealPair) <= (case #1 revealPair of
+                        "red" => maxRed
+                      | "green" => maxGreen
+                      | "blue" => maxBlue
+                  ))
+                  revealPairs
+              end
+            )
+            rounds
+        end
+      )
+      lines
+  end
+
+val result = List.foldl
+  (fn (game, acc) =>
+    let
+      val title = List.hd (String.tokens (equals #":") game)
+      val id = Option.valOf (Int.fromString (String.extract (title, 5, NONE)))
+    in
+      acc + id
+    end
+  )
+  0
+  possibleGames