diff --git a/15.nix b/15.nix
new file mode 100644
index 0000000..3db6c09
--- /dev/null
+++ b/15.nix
@@ -0,0 +1,18 @@
+with import <nixpkgs> { };
+with stdenv.lib;
+let
+  attr = {a="a"; b = 1; c = true;};
+  s = "b";
+in
+{
+  #replace all X, everything should evaluate to true
+  ex0 = isAttrs attr;
+  ex1 = attr.a == "a";
+  ex2 = attr.${s} == 1;
+  ex3 = attrVals ["c" "b"] attr == [ true 1 ];
+  ex4 = attrValues attr == [ "a" 1 true ];
+  ex5 = builtins.intersectAttrs attr {a="b"; d=234; c="";} 
+    == { a = "b"; c = "";};
+  ex6 = removeAttrs attr ["b" "c"] == { a="a"; };
+  ex7 = ! attr ? a == false;
+}
\ No newline at end of file