day 4

4/advanced.nix

@@ -0,0 +1,31 @@
+with import ../lib;
+
+let
+  input = fileContents ./input.txt;
+
+  bounding' = get1: get2: let
+    a1 = get1 0;
+    a2 = get1 1;
+    b1 = get2 0;
+    b2 = get2 1;
+  in
+    a1 <= b1 && a2 >= b1 ||
+    a2 >= b2 && a1 <= b2;
+
+  bounding = get1: get2: (bounding' get1 get2) || (bounding' get2 get1);
+in
+
+pipe input [
+  (splitStr "\n")
+  (map (flip pipe [
+    (splitStr ",")
+    (map (flip pipe [
+      (splitStr "-")
+      (map toInt)
+      elemAt
+    ]))
+    (uncurry bounding)
+  ]))
+  (filter id)
+  length
+]

4/basic.nix

@@ -0,0 +1,25 @@
+with import ../lib;
+
+let
+  input = fileContents ./input.txt;
+
+  bounding' = get1: get2: (get1 0) <= (get2 0) && (get1 1) >= (get2 1);
+
+  bounding = get1: get2: (bounding' get1 get2) || (bounding' get2 get1);
+in
+
+pipe input [
+  (splitStr "\n")
+  (map (flip pipe [
+    (splitStr ",")
+    (map (flip pipe [
+      (splitStr "-")
+      (map toInt)
+      elemAt
+    ]))
+    elemAt
+    (get: bounding (get 0) (get 1))
+  ]))
+  (filter id)
+  length
+]

lib/default.nix

@@ -15,6 +15,11 @@ let
 
     sum = foldl1 add;
 
+    uncurry = f: xs: pipe xs [
+      elemAt
+      (get: f (get 0) (get 1))
+    ];
+
     unpackAttrsCall = f: attrs: f attrs.a attrs.b;
   };
 in nixpkgsLib.fix aocLib