diff --git a/default.nix b/default.nix
index 0c9248a..35a779a 100644
--- a/default.nix
+++ b/default.nix
@@ -3,16 +3,8 @@
 # if evaluating inside the store, import the outputs.nix file
 
 let
-  contains = str: substr: let
-    str_length = builtins.stringLength str;
-    substr_length = builtins.stringLength substr;
-    listOfPossibleSubstrings = builtins.genList (i: builtins.substring i substr_length str) (str_length - substr_length + 1);
-  in if substr_length > str_length then false else builtins.any (x: x == substr) listOfPossibleSubstrings;
-
-  endsWith = str: substr: let
-    str_length = builtins.stringLength str;
-    substr_length = builtins.stringLength substr;
-  in if substr_length > str_length then false else builtins.substring (str_length - substr_length) str_length str == substr;
+  # Ideally this file should not depend on nixpkgs lib itself, but I like the utilities here
+  lib = (import "${(import ./inputs.nix {}).nixpkgs}/lib");
 
   gitignore = builtins.filter (v:
       # ignore comments and empty lines
@@ -32,11 +24,11 @@ let
       if pattern == "*" then true
       else if pattern == ".*" then true
       else if pattern == "*.*" then true
-      else if builtins.substring 0 2 pattern == "*." then endsWith path (builtins.substring 0 2 pattern)
-      else if contains pattern "*" then abort unsupportedPatternMessage
+      else if builtins.substring 0 2 pattern == "*." then lib.hasSuffix (builtins.substring 0 2 pattern) path
+      else if lib.hasInfix "*" pattern then abort unsupportedPatternMessage
       else if patternLength > 2 && builtins.substring 0 2 pattern == "./" then abort unsupportedPatternMessage
       else if patternLength > 1 && builtins.substring 0 1 pattern == "/" then abort unsupportedPatternMessage
-      else contains path pattern
+      else lib.hasInfix pattern path
   ) gitignore;
 
   currentFilePath = (builtins.unsafeGetAttrPos "any" { any = "any"; }).file;