From c660e30a7dd781f71bed050b20c3e2d0b069e063 Mon Sep 17 00:00:00 2001
From: Jesper Louis Andersen <jesper.louis.andersen@gmail.com>
Date: Sat, 9 Apr 2016 17:17:59 +0200
Subject: Implement lists:join/2

Add a call which works much like string:join/2 but for arbitrary lists. Provide
the function itself, lifted from Haskells Data.List standard library, provide
documentation and provide tests for the function.
---
 lib/stdlib/src/lists.erl | 15 ++++++++++++++-
 1 file changed, 14 insertions(+), 1 deletion(-)

(limited to 'lib/stdlib/src')

diff --git a/lib/stdlib/src/lists.erl b/lib/stdlib/src/lists.erl
index 2b4472cdf7..af9d63ddd6 100644
--- a/lib/stdlib/src/lists.erl
+++ b/lib/stdlib/src/lists.erl
@@ -39,7 +39,8 @@
 -export([all/2,any/2,map/2,flatmap/2,foldl/3,foldr/3,filter/2,
 	 partition/2,zf/2,filtermap/2,
 	 mapfoldl/3,mapfoldr/3,foreach/2,takewhile/2,dropwhile/2,splitwith/2,
-	 split/2]).
+	 split/2,
+	 join/2]).
 
 %%% BIFs
 -export([keyfind/3, keymember/3, keysearch/3, member/2, reverse/2]).
@@ -1439,6 +1440,18 @@ split(N, [H|T], R) ->
 split(_, [], _) ->
     badarg.
 
+-spec join(Sep, List1) -> List2 when
+      Sep :: T,
+      List1 :: [T],
+      List2 :: [T],
+      T :: term().
+
+join(_Sep, []) -> [];
+join(Sep, [H|T]) -> [H|join_prepend(Sep, T)].
+
+join_prepend(_Sep, []) -> [];
+join_prepend(Sep, [H|T]) -> [Sep,H|join_prepend(Sep,T)].
+
 %%% =================================================================
 %%% Here follows the implementation of the sort functions.
 %%%
-- 
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