Add -flatten

README.md

@@ -18,6 +18,7 @@ Or you can just dump `dash.el` in your load path somewhere.
 * [-filter](#filter-fn-list) `(fn list)`
 * [-remove](#remove-fn-list) `(fn list)`
 * [-keep](#keep-fn-list) `(fn list)`
+* [-flatten](#flatten-l) `(l)`
 * [-concat](#concat-rest-lists) `(&rest lists)`
 * [-mapcat](#mapcat-fn-list) `(fn list)`
 * [-take](#take-n-list) `(n list)`
@@ -146,6 +147,15 @@ Returns a new list of the non-nil results of applying `fn` to the items in `list
 (--keep (when (> it 3) (* 10 it)) '(1 2 3 4 5 6)) ;; => '(40 50 60)
 ```
 
+### -flatten `(l)`
+
+Takes a nested list `l` and returns its contents as a single, flat list.
+
+```cl
+(-flatten '((1))) ;; => '(1)
+(-flatten '((1 (2 3) (((4 (5))))))) ;; => '(1 2 3 4 5)
+```
+
 ### -concat `(&rest lists)`
 
 Returns a new list with the concatenation of the elements in

dash.el

@@ -130,6 +130,12 @@ Alias: `-reject'"
   "Returns a new list of the non-nil results of applying FN to the items in LIST."
   (--keep (funcall fn it) list))
 
+(defun -flatten (l)
+  "Takes a nested list L and returns its contents as a single, flat list."
+  (if (listp l)
+      (-mapcat '-flatten l)
+    (list l)))
+
 (defun -concat (&rest lists)
   "Returns a new list with the concatenation of the elements in
 the supplied LISTS."

examples.el

@@ -47,6 +47,10 @@
   (-keep (lambda (num) (when (> num 3) (* 10 num))) '(1 2 3 4 5 6)) => '(40 50 60)
   (--keep (when (> it 3) (* 10 it)) '(1 2 3 4 5 6)) => '(40 50 60))
 
+(defexamples -flatten
+  (-flatten '((1))) => '(1)
+  (-flatten '((1 (2 3) (((4 (5))))))) => '(1 2 3 4 5))
+
 (defexamples -concat
   (-concat '(1)) => '(1)
   (-concat '(1) '(2)) => '(1 2)