add vary-meta

Author: mpenet

pixie/stdlib.pxi

@@ -2717,3 +2717,9 @@ Calling this function on something that is not ISeqable returns a seq with that
   (if (satisfies? IComparable x)
     (-compare x y)
     (throw [::ComparisonError (str x " does not satisfy IComparable")])))
+
+(defn vary-meta
+  [x f & args]
+  "Returns x with meta data updated with the application of f and args to it.
+ex: (vary-meta x assoc :foo 42)"
+  (with-meta x (apply f (meta x) args)))

tests/pixie/tests/test-stdlib.pxi

@@ -691,3 +691,6 @@
     (t/assert= m (map-entry :a 1))
     (t/assert= m [:a 1])
     (t/assert= m '(:a 1))))
+
+(t/deftest vary-meta
+  (t/assert= 42 (-> {} (vary-meta assoc :foo 42) meta :foo)))