Adding operators DSL in order to use Clojure functions instead of hashes.

Casbah has a similar concept called Bareword Operators.
Korma uses operators a bit differently, but idea is quite same, too. 

One of the obvious advantages is that you can make sure you didn't screw make a typo 
in operator name during compile-time. Plus, we can guarantee that there is a subset
of used / supported operators, and add them gradually, keeping track of them in one place, 
which will simplify tests, too.

src/monger/operators.clj

@@ -0,0 +1,28 @@
+(ns monger.operators)
+
+(defmacro defoperator
+  [operator]
+  (let [operator-name (symbol (str operator))]
+  `(defn ~operator-name
+     [arg#]
+     { (str '~operator-name) arg# }
+        )))
+(defoperator $gt)
+(defoperator $inc)
+(defoperator $set)
+(defoperator $unset)
+
+;; $lt
+;; $lte
+;; $all
+;; $in
+;; $set
+;; $unset
+;; $inc
+;; $push
+;; $pushAll
+;; $addToSet
+;; $pop
+;; $pull
+;; $pullAll
+;; $rename

test/monger/test/atomic_modifiers.clj

@@ -3,14 +3,16 @@
 (ns monger.test.atomic-modifiers
   (:import  [com.mongodb WriteResult WriteConcern DBCursor DBObject CommandResult$CommandFailure]
             [org.bson.types ObjectId]
-            [java.util Date])
+            [java.util Date]
+
+            )
   (:require [monger core util]
             [monger.collection :as mgcol]
             [monger.result     :as mgres])
   (:use [clojure.test]
+        [monger.operators]
         [monger.test.fixtures]))
 
-
 (defn purge-scores-collection
   [f]
   (purge-collection "scores" f))
@@ -28,8 +30,9 @@
 (deftest increment-a-single-existing-field-using-$inc-modifier
   (let [coll "scores"
         oid  (ObjectId.)]
+    (println ($inc { :score 20 } ))
     (mgcol/insert coll { :_id oid :username "l33r0y" :score 100 })
-    (mgcol/update coll { :_id oid } { "$inc" { :score 20 } })
+    (mgcol/update coll { :_id oid } ($inc { :score 20 } ))
     (is (= 120 (:score (mgcol/find-map-by-id coll oid))))))
 
 
@@ -37,7 +40,7 @@
   (let [coll "scores"
         oid  (ObjectId.)]
     (mgcol/insert coll { :_id oid :username "l33r0y" })
-    (mgcol/update coll { :_id oid } { "$inc" { :score 30 } })
+    (mgcol/update coll { :_id oid } ($inc { :score 30 } ))
     (is (= 30 (:score (mgcol/find-map-by-id coll oid))))))
 
 
@@ -45,7 +48,7 @@
   (let [coll "scores"
         oid  (ObjectId.)]
     (mgcol/insert coll { :_id oid :username "l33r0y" :score 100 :bonus 0 })
-    (mgcol/update coll { :_id oid } { "$inc" { :score 20 :bonus 10 } })
+    (mgcol/update coll { :_id oid } ($inc { :score 20 :bonus 10 } ))
     (is (= { :_id oid :score 120 :bonus 10 :username "l33r0y" } (mgcol/find-map-by-id coll oid)))))
 
 
@@ -53,7 +56,7 @@
   (let [coll "scores"
         oid  (ObjectId.)]
     (mgcol/insert coll { :_id oid :username "l33r0y" :score 100 })
-    (mgcol/update coll { :_id oid } { "$inc" { :score 20 :bonus 10 } })
+    (mgcol/update coll { :_id oid } ($inc { :score 20 :bonus 10 } ))
     (is (= { :_id oid :score 120 :bonus 10 :username "l33r0y" } (mgcol/find-map-by-id coll oid)))))
 
 
@@ -66,21 +69,21 @@
   (let [coll "things"
         oid  (ObjectId.)]
     (mgcol/insert coll { :_id oid :weight 10.0 })
-    (mgcol/update coll { :_id oid } { "$set" { :weight 20.5 } })
+    (mgcol/update coll { :_id oid } ( $set { :weight 20.5 } ))
     (is (= 20.5 (:weight (mgcol/find-map-by-id coll oid [:weight]))))))
 
 (deftest set-a-single-non-existing-field-using-$set-modifier
   (let [coll "things"
         oid  (ObjectId.)]
     (mgcol/insert coll { :_id oid :weight 10.0 })
-    (mgcol/update coll { :_id oid } { "$set" { :height 17.2 } })
+    (mgcol/update coll { :_id oid } ( $set { :height 17.2 } ))
     (is (= 17.2 (:height (mgcol/find-map-by-id coll oid [:height]))))))
 
 (deftest update-multiple-existing-fields-using-$set-modifier
   (let [coll "things"
         oid  (ObjectId.)]
     (mgcol/insert coll { :_id oid :weight 10.0 :height 15.2 })
-    (mgcol/update coll { :_id oid } { "$set" { :weight 20.5 :height 25.6 } })
+    (mgcol/update coll { :_id oid } ( $set { :weight 20.5 :height 25.6 } ))
     (is (= { :_id oid :weight 20.5 :height 25.6 } (mgcol/find-map-by-id coll oid [:weight])))))
 
 
@@ -88,7 +91,7 @@
   (let [coll "things"
         oid  (ObjectId.)]
     (mgcol/insert coll { :_id oid :weight 10.0 })
-    (mgcol/update coll { :_id oid } { "$set" { :weight 20.5 :height 25.6 } })
+    (mgcol/update coll { :_id oid } ($set { :weight 20.5 :height 25.6 } ))
     (is (= { :_id oid :weight 20.5 :height 25.6 } (mgcol/find-map-by-id coll oid [:weight])))))
 
 
@@ -100,7 +103,7 @@
   (let [coll "docs"
         oid  (ObjectId.)]
     (mgcol/insert coll { :_id oid :title "Document 1" :published true })
-    (mgcol/update coll { :_id oid } { "$unset" { :published 1 } })
+    (mgcol/update coll { :_id oid } ( $unset { :published 1 } ))
     (is (= { :_id oid :title "Document 1" } (mgcol/find-map-by-id coll oid)))))
 
 
@@ -108,7 +111,7 @@
   (let [coll "docs"
         oid  (ObjectId.)]
     (mgcol/insert coll { :_id oid :title "Document 1" :published true :featured true })
-    (mgcol/update coll { :_id oid } { "$unset" { :published 1 :featured true } })
+    (mgcol/update coll { :_id oid } ( $unset { :published 1 :featured true } ))
     (is (= { :_id oid :title "Document 1" } (mgcol/find-map-by-id coll oid)))))
 
 
@@ -116,7 +119,7 @@
   (let [coll "docs"
         oid  (ObjectId.)]
     (mgcol/insert coll { :_id oid :title "Document 1" :published true })
-    (is (mgres/ok? (mgcol/update coll { :_id oid } { "$unset" { :published 1 :featured true } })))
+    (is (mgres/ok? (mgcol/update coll { :_id oid } ( $unset { :published 1 :featured true } ))))
     (is (= { :_id oid :title "Document 1" } (mgcol/find-map-by-id coll oid)))))