From f605167a53e829e51983b3fdacac45435c9af8cf Mon Sep 17 00:00:00 2001
From: Nathan Marz <nathan@nathanmarz.com>
Date: Thu, 9 Jun 2016 16:36:20 -0400
Subject: [PATCH] implement traverse

---
 scripts/benchmarks.clj             | 10 ++++++++++
 src/clj/com/rpl/specter.cljx       | 11 +++++++++++
 src/clj/com/rpl/specter/impl.cljx  | 14 ++++++++++++++
 src/clj/com/rpl/specter/macros.clj |  9 +++++++++
 4 files changed, 44 insertions(+)

diff --git a/scripts/benchmarks.clj b/scripts/benchmarks.clj
index cf80a41..7dc0450 100644
--- a/scripts/benchmarks.clj
+++ b/scripts/benchmarks.clj
@@ -52,6 +52,15 @@
        (println "\n********************************\n")
        )))
 
+(let [data (range 1000)]
+  (run-benchmark "Traverse into a set" 5000
+    (set data)
+    (set (select ALL data))
+    (persistent!
+      (reduce conj! (transient #{}) (traverse ALL data)))
+    (reduce conj #{} (traverse ALL data))
+    ))
+
 (let [data {:a {:b {:c 1}}}
       p (comp-paths :a :b :c)]
   (run-benchmark "get value in nested map" 5000000
@@ -243,3 +252,4 @@
     2000000
     (vary-meta data assoc :y 2)
     (setval [META :y] 2 data)))
+
diff --git a/src/clj/com/rpl/specter.cljx b/src/clj/com/rpl/specter.cljx
index 9d185ac..f7b60da 100644
--- a/src/clj/com/rpl/specter.cljx
+++ b/src/clj/com/rpl/specter.cljx
@@ -104,6 +104,17 @@
   [path structure]
   (compiled-selected-any? (i/comp-paths* path) structure))
 
+;; Reducible traverse functions
+
+(def ^{:doc "Version of traverse that takes in a path pre-compiled with comp-paths"}
+  compiled-traverse i/do-compiled-traverse)
+
+(defn traverse*
+  "Return a reducible object that traverses over `structure` to every element
+   specified by the path"
+  [apath structure]
+  (compiled-traverse (i/comp-paths* apath) structure))
+
 ;; Transformation functions
 
 (def ^{:doc "Version of transform that takes in a path pre-compiled with comp-paths"}
diff --git a/src/clj/com/rpl/specter/impl.cljx b/src/clj/com/rpl/specter/impl.cljx
index ffddf99..5ac024c 100644
--- a/src/clj/com/rpl/specter/impl.cljx
+++ b/src/clj/com/rpl/specter/impl.cljx
@@ -653,6 +653,20 @@
       structure)
     ))
 
+(defn do-compiled-traverse [apath structure]
+  (reify clojure.lang.IReduceInit
+    (reduce [this afn start]
+      (let [cell (mutable-cell start)]
+        (compiled-traverse*
+          apath
+          (fn [elem]
+            (let [curr (get-cell cell)]
+              (set-cell! cell (afn curr elem))
+              ))
+          structure
+          )
+        (get-cell cell)
+        ))))
 
 (defn compiled-select* [path structure]
   (let [res (mutable-cell (transient []))
diff --git a/src/clj/com/rpl/specter/macros.clj b/src/clj/com/rpl/specter/macros.clj
index c87a29e..a5d757f 100644
--- a/src/clj/com/rpl/specter/macros.clj
+++ b/src/clj/com/rpl/specter/macros.clj
@@ -599,6 +599,15 @@
   [apath aval structure]
   `(i/compiled-setval* (path ~apath) ~aval ~structure))
 
+(defmacro traverse
+  "Return a reducible object that traverses over `structure` to every element
+   specified by the path.
+   This macro will attempt to do inline factoring and caching of the path, falling
+   back to compiling the path on every invocation it it's not possible to 
+   factor/cache the path."
+  [apath structure]
+  `(i/do-compiled-traverse (path ~apath) ~structure))
+
 (defmacro replace-in
   "Similar to transform, except returns a pair of [transformed-structure sequence-of-user-ret].
    The transform-fn in this case is expected to return [ret user-ret]. ret is