huge speedup to if-path when condition is a single statically known function, big optimization for all transforms that don't use value collection by using identical? instead of empty?

project.clj

@@ -1,7 +1,9 @@
 (def VERSION (.trim (slurp "VERSION")))
 
 (defproject com.rpl/specter VERSION
-  :jvm-opts ["-XX:-OmitStackTraceInFastThrow"] ; this prevents JVM from doing optimizations which can remove stack traces from NPE and other exceptions
+  :jvm-opts ["-XX:-OmitStackTraceInFastThrow" ; this prevents JVM from doing optimizations which can remove stack traces from NPE and other exceptions
+             ;"-agentpath:/Applications/YourKit_Java_Profiler_2015_build_15056.app/Contents/Resources/bin/mac/libyjpagent.jnilib"
+             ] 
   :source-paths ["src/clj"]
   :java-source-paths ["src/java"]
   :test-paths ["test", "target/test-classes"]

src/clj/com/rpl/specter.cljx

@@ -506,20 +506,23 @@
 (defpathedfn if-path
   "Like cond-path, but with if semantics."
   ([cond-p then-path]
-    (fixed-pathed-nav [late-cond cond-p
-                       late-then then-path]
-      (select* [this structure next-fn]
-        (i/if-select structure next-fn late-cond late-then STOP))
-      (transform* [this structure next-fn]
-        (i/if-transform structure next-fn late-cond late-then STOP))))
+    (if-path cond-p then-path STOP))
   ([cond-p then-path else-path]
+    (if-let [afn (i/extract-basic-filter-fn cond-p)]
+      (fixed-pathed-nav [late-then then-path
+                         late-else else-path]
+        (select* [this structure next-fn]
+          (i/if-select structure next-fn afn late-then late-else))
+        (transform* [this structure next-fn]
+          (i/if-transform structure next-fn afn late-then late-else)))
       (fixed-pathed-nav [late-cond cond-p
                          late-then then-path
                          late-else else-path]
         (select* [this structure next-fn]
-        (i/if-select structure next-fn late-cond late-then late-else))
+          (i/if-select structure next-fn #(i/selected?* late-cond %) late-then late-else))
         (transform* [this structure next-fn]
-        (i/if-transform structure next-fn late-cond late-then late-else)))))
+          (i/if-transform structure next-fn #(i/selected?* late-cond %) late-then late-else))
+        ))))
 
 (defpathedfn cond-path
   "Takes in alternating cond-path path cond-path path...

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

@@ -93,11 +93,11 @@
     (fn [params params-idx selector structure]
       (selector params params-idx [] structure
         (fn [_ _ vals structure]
-          (if-not (empty? vals) [(conj vals structure)] [structure]))))
+          (if-not (identical? [] vals) [(conj vals structure)] [structure]))))
     (fn [params params-idx transformer transform-fn structure]
       (transformer params params-idx [] structure
         (fn [_ _ vals structure]
-          (if (empty? vals)
+          (if (identical? [] vals)
             (transform-fn structure)
             (apply transform-fn (conj vals structure))))))
     ))
@@ -757,17 +757,28 @@
     (next-fn structure)
     ))
 
-(defn if-select [structure next-fn late-cond late-then late-else]
-  (let [apath (if (empty? (compiled-select* late-cond structure))
-                late-else
-                late-then)]
+(defn extract-basic-filter-fn [path]
+  (cond (fn? path)
+        path
+
+        (and (coll? path)
+             (= 1 (count path))
+             (fn? (first path)))
+        (first path)
+    ))
+
+
+(defn if-select [structure next-fn then-tester late-then late-else]
+  (let [apath (if (then-tester structure)
+                late-then
+                late-else)]
     (doall (mapcat next-fn (compiled-select* apath structure)))
     ))
 
-(defn if-transform [structure next-fn late-cond late-then late-else]
-  (let [apath (if (empty? (compiled-select* late-cond structure))
-                late-else
-                late-then)]
+(defn if-transform [structure next-fn then-tester late-then late-else]
+  (let [apath (if (then-tester structure)
+                late-then
+                late-else)]
     (compiled-transform* apath next-fn structure)
     ))