added view and viewfn

src/clj/com/rpl/specter.clj

@@ -102,6 +102,11 @@
 
 (defn keypath [akey] (->KeyPath akey))
 
+(defn view [afn] (->ViewPath afn))
+
+(defmacro viewfn [& args]
+  `(view (fn ~@args)))
+
 (extend-type clojure.lang.Keyword
   StructurePath
   (select* [kw structure next-fn]

src/clj/com/rpl/specter/impl.clj

@@ -232,7 +232,6 @@
     (key-update akey structure next-fn)
     ))
 
-
 (deftype SelectorValsPath [sel-fn selector]
   ValPath
   (select-val [this structure]
@@ -257,3 +256,11 @@
         (vec res)
         res
         ))))
+
+(deftype ViewPath [view-fn]
+  StructurePath
+  (select* [this structure next-fn]
+    (-> structure view-fn next-fn))
+  (update* [this structure next-fn]
+    (-> structure view-fn next-fn)
+    ))

test/clj/com/rpl/specter/core_test.clj

@@ -210,3 +210,13 @@
   (is (= 3 (select-one :b {:a 1 :b 3})))
   (is (= 5 (select-one (comp-structure-paths :a :b) {:a {:b 5}})))
   )
+
+(defspec view-test
+  (for-all+
+    [i gen/int
+     afn (gen/elements [inc dec])]
+    (= (first (select (view afn) i))
+       (first (select (viewfn [i] (afn i)) i))
+       (afn i)
+       (update (view afn) identity i)
+       )))