Add fold term

src/rethinkdb/query.cljc

@@ -459,6 +459,11 @@
   [sq x-or-func]
   (term :CONTAINS [sq x-or-func]))
 
+(defn fold
+  "Apply a function to a sequence in order, maintaining state via an accumulator. 
+  The fold command returns either a single value or a new sequence."
+  [sq base func & [optargs]] (term :FOLD [sq base func] optargs))
+
 ;;; Document manipulation
 
 (defn pluck

src/rethinkdb/types.cljc

@@ -86,6 +86,7 @@
                        "LIMIT" 71,
                        "OFFSETS_OF" 87,
                        "CONTAINS" 93,
+                       "FOLD" 187,
                        "GET_FIELD" 31,
                        "KEYS" 94,
                        "VALUES" 186,

test/rethinkdb/core_test.clj

@@ -230,7 +230,15 @@
       (r/max [4 6]) 6
       (r/distinct [1 6 1 8]) [1 6 8]
       (r/contains [1 6 1 8] 1) true
-      (r/contains [1 6 1 8] 2) false)))
+      (r/contains [1 6 1 8] 2) false
+      (r/fold [1 6 1 8] 0 (r/fn [acc number] (r/add acc number))) 16
+      (r/fold [1 6 1 8] 0 (r/fn [acc number] (r/add acc 1))  ; increment accumulator
+              {:emit (r/fn [acc number new-acc]
+                       (r/branch (-> new-acc (r/mod 2) (r/eq 0))
+                                 [number]
+                                 [])) ; select elements on even positions
+               :final-emit (r/fn [acc] [100])}) [6 8 100] ; append 100 to the end
+      )))
 
 (deftest changefeeds
   (with-open [conn (r/connect)]