Solve day 2 part 1

day_2.sml

@@ -0,0 +1,23 @@
+fun isDecreasing (l: int list) : bool =
+    ListPair.all (fn (a, b) => b < a andalso b >= a - 3) (l, tl l)
+
+fun isIncreasing (l: int list) : bool =
+    ListPair.all (fn (a, b) => b > a andalso b <= a + 3) (l, tl l)
+
+val file = TextIO.openIn "day_2.txt"
+val input = TextIO.inputAll file;
+TextIO.closeIn file;
+
+val lines = String.tokens (fn (char) => char = #"\n") input
+
+val reports = map
+    (fn (line) =>
+        let val numbers = String.tokens Char.isSpace line
+        in map (fn (n) => valOf (Int.fromString n)) numbers end
+    )
+    lines
+
+val safeReports = List.filter (fn (report) => isDecreasing report orelse isIncreasing report) reports
+
+val safeAmount = List.length safeReports
+