From 0515b711dfb3f5b2e650cd158addbb32d92ca525 Mon Sep 17 00:00:00 2001
From: Christophe Grand <christophe@cgrand.net>
Date: Thu, 26 Oct 2017 18:09:32 +0200
Subject: [PATCH] 0.13.0 x/without, the opposite of x/into: dissoc/disj'ing
 instead of conj'ing.

---
 README.md                        |  6 +++---
 project.clj                      |  2 +-
 src/net/cgrand/xforms.cljc       | 36 ++++++++++++++++++++++++++++++++
 test/net/cgrand/xforms_test.cljc |  4 ++++
 4 files changed, 44 insertions(+), 4 deletions(-)

diff --git a/README.md b/README.md
index 0973d00..92e2cb0 100644
--- a/README.md
+++ b/README.md
@@ -12,7 +12,7 @@ In `net.cgrand.xforms`:
 
  * regular ones: `partition` (1 arg), `reductions`, `for`, `take-last`, `drop-last`, `window` and `window-by-time`
  * higher-order ones: `by-key`, `into-by-key`, `multiplex`, `transjuxt`, `partition` (2+ args)
- * 1-item ones: `reduce`, `into`, `transjuxt`, `last`, `count`, `avg`, `sd`, `min`, `minimum`, `max`, `maximum`, `str`
+ * 1-item ones: `reduce`, `into`, `without`, `transjuxt`, `last`, `count`, `avg`, `sd`, `min`, `minimum`, `max`, `maximum`, `str`
 
 In `net.cgrand.xforms.io`:
  * `sh` to use any process as a transducer
@@ -27,7 +27,7 @@ In `net.cgrand.xforms.io`:
 
 *Transducing contexts*:
 
- * in `net.cgrand.xforms`: `transjuxt` (for performing several transductions in a single pass), `iterator` (clojure only), `into`, `count` and `some`.
+ * in `net.cgrand.xforms`: `transjuxt` (for performing several transductions in a single pass), `iterator` (clojure only), `into`, `without`, `count` and `some`.
  * in `net.cgrand.xforms.io`: `line-out` (3+ args) and `edn-out` (3+ args).
 
 *Reducible views* (in `net.cgrand.xforms.io`): `lines-in` and `edn-in`.
@@ -37,7 +37,7 @@ In `net.cgrand.xforms.io`:
 Add this dependency to your project:
 
 ```clj
-[net.cgrand/xforms "0.12.1"]
+[net.cgrand/xforms "0.13.0"]
 ```
 
 ```clj
diff --git a/project.clj b/project.clj
index cafbad6..b969a04 100644
--- a/project.clj
+++ b/project.clj
@@ -1,4 +1,4 @@
-(defproject net.cgrand/xforms "0.12.2"
+(defproject net.cgrand/xforms "0.13.0"
   :description "Extra transducers for Clojure"
   :url "https://github.com/cgrand/xforms"
   :license {:name "Eclipse Public License"
diff --git a/src/net/cgrand/xforms.cljc b/src/net/cgrand/xforms.cljc
index f5dc0cf..6d42da1 100644
--- a/src/net/cgrand/xforms.cljc
+++ b/src/net/cgrand/xforms.cljc
@@ -196,6 +196,42 @@
         (rf (core/reduce-kv rf (rf) from))
         (rf (core/reduce rf (rf) from))))))
 
+(defn- without-rf [from]
+  (cond
+    #?(:clj (instance? clojure.lang.IEditableCollection from)
+        :cljs (satisfies? IEditableCollection from))
+    (if (map? from)
+      (fn
+        ([] (transient from))
+        ([acc] (persistent! acc))
+        ([acc x] (dissoc! acc x)))
+      (fn
+        ([] (transient from))
+        ([acc] (persistent! acc))
+        ([acc x] (disj! acc x))))
+    (map? from)
+    (fn
+      ([] from)
+      ([acc] acc)
+      ([acc x] (dissoc acc x)))
+    :else
+    (fn
+      ([] from)
+      ([acc] acc)
+      ([acc x] (disj acc x)))))
+
+(defn without
+  "The opposite of x/into: dissociate or disjoin from the target."
+  ([target]
+    (reduce (without-rf target)))
+  ([target keys]
+    (without target identity keys))
+  ([target xform keys]
+    (let [rf (xform (without-rf target))]
+      (if-let [rf (and (map? keys) (kvreducible? keys) (some-kvrf rf))]
+        (rf (core/reduce-kv rf (rf) keys))
+        (rf (core/reduce rf (rf) keys))))))
+
 (defn minimum
   ([comparator]
     (minimum comparator nil))
diff --git a/test/net/cgrand/xforms_test.cljc b/test/net/cgrand/xforms_test.cljc
index 708d0a5..be3b9c8 100644
--- a/test/net/cgrand/xforms_test.cljc
+++ b/test/net/cgrand/xforms_test.cljc
@@ -90,6 +90,10 @@
   (is (= (into [] (comp (x/partition 2 2 nil) (x/into [])) (range 8))
         [[[0 1] [2 3] [4 5] [6 7]]])))
 
+(deftest without
+  (is (= {0 :ok 2 :ok 4 :ok 6 :ok 8 :ok} (x/without (zipmap (range 10) (repeat :ok)) (filter odd?) (range 20))))
+  (is (= #{0 2 4 6 8 } (x/without (set (range 10)) (filter odd?) (range 20)))))
+
 #?(:clj
     (deftest iterator
       (is (true? (.hasNext (x/iterator x/count (.iterator (range 5))))))