Add -separate (thanks @Fuco1)

README.md

@@ -35,6 +35,7 @@ Or you can just dump `dash.el` in your load path somewhere.
 * [-drop-while](#-drop-while-pred-list) `(pred list)`
 * [-split-at](#-split-at-n-list) `(n list)`
 * [-split-with](#-split-with-pred-list) `(pred list)`
+* [-separate](#-separate-pred-list) `(pred list)`
 * [-partition](#-partition-n-list) `(n list)`
 * [-partition-all](#-partition-all-n-list) `(n list)`
 * [-partition-by](#-partition-by-fn-list) `(fn list)`
@@ -331,6 +332,16 @@ Returns a list of ((-take-while `pred` `list`) (-drop-while `pred` `list`))
 (--split-with (< it 4) '(1 2 3 4 3 2 1)) ;; => '((1 2 3) (4 3 2 1))
 ```
 
+### -separate `(pred list)`
+
+Returns a list of ((-filter `pred` `list`) (-remove `pred` `list`)).
+
+```cl
+(-separate (lambda (num) (= 0 (% num 2))) '(1 2 3 4 5 6 7)) ;; => '((2 4 6) (1 3 5 7))
+(--separate (< it 5) '(3 7 5 9 3 2 1 4 6)) ;; => '((3 3 2 1 4) (7 5 9 6))
+(-separate 'cdr '((1 2) (1) (1 2 3) (4))) ;; => '(((1 2) (1 2 3)) ((1) (4)))
+```
+
 ### -partition `(n list)`
 
 Returns a new list with the items in `list` grouped into `n-`sized sublists.

dash.el

@@ -335,6 +335,18 @@ Returns `nil` both if all items match the predicate, and if none of the items ma
   "Returns a list of ((-take-while PRED LIST) (-drop-while PRED LIST))"
   (--split-with (funcall pred it) list))
 
+(defmacro --separate (form list)
+  "Anaphoric form of `-separate'."
+  (let ((y (make-symbol "yes"))
+        (n (make-symbol "no")))
+    `(let (,y ,n)
+       (--each ,list (if ,form (!cons it ,y) (!cons it ,n)))
+       (list (nreverse ,y) (nreverse ,n)))))
+
+(defun -separate (pred list)
+  "Returns a list of ((-filter PRED LIST) (-remove PRED LIST))."
+  (--separate (funcall pred it) list))
+
 (defun -partition (n list)
   "Returns a new list with the items in LIST grouped into N-sized sublists.
 If there are not enough items to make the last group N-sized,

examples.el

@@ -130,6 +130,11 @@
   (-split-with 'even? '(2 4 5 6)) => '((2 4) (5 6))
   (--split-with (< it 4) '(1 2 3 4 3 2 1)) => '((1 2 3) (4 3 2 1)))
 
+(defexamples -separate
+  (-separate (lambda (num) (= 0 (% num 2))) '(1 2 3 4 5 6 7)) => '((2 4 6) (1 3 5 7))
+  (--separate (< it 5) '(3 7 5 9 3 2 1 4 6)) => '((3 3 2 1 4) (7 5 9 6))
+  (-separate 'cdr '((1 2) (1) (1 2 3) (4))) => '(((1 2) (1 2 3)) ((1) (4))))
+
 (defexamples -partition
   (-partition 2 '(1 2 3 4 5 6)) => '((1 2) (3 4) (5 6))
   (-partition 2 '(1 2 3 4 5 6 7)) => '((1 2) (3 4) (5 6))