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.

1 files changed, 15 insertions, 1 deletions

diff --git a/lib/stdlib/test/lists_SUITE.erl b/lib/stdlib/test/lists_SUITE.erl
index b21eb37ee3..f3711c569e 100644
--- a/lib/stdlib/test/lists_SUITE.erl
+++ b/lib/stdlib/test/lists_SUITE.erl
@@ -55,6 +55,7 @@
 	 ufunsort_error/1,
 	 zip_unzip/1, zip_unzip3/1, zipwith/1, zipwith3/1,
 	 filter_partition/1, 
+	 join/1,
 	 otp_5939/1, otp_6023/1, otp_6606/1, otp_7230/1,
 	 suffix/1, subtract/1, droplast/1, hof/1]).
 
@@ -119,7 +120,7 @@ groups() ->
      {tickets, [parallel], [otp_5939, otp_6023, otp_6606, otp_7230]},
      {zip, [parallel], [zip_unzip, zip_unzip3, zipwith, zipwith3]},
      {misc, [parallel], [reverse, member, dropwhile, takewhile,
-			 filter_partition, suffix, subtract,
+			 filter_partition, suffix, subtract, join,
 			 hof]}
     ].
 
@@ -2413,6 +2414,19 @@ zipwith3(Config) when is_list(Config) ->
 
     ok.
 
+%% Test lists:join/2
+join(Config) when is_list(Config) ->
+    A = [a,b,c],
+    Sep = x,
+    [a,x,b,x,c] = lists:join(Sep, A),
+
+    B = [b],
+    [b] = lists:join(Sep, B),
+
+    C = [],
+    [] = lists:join(Sep, C),
+    ok.
+
 %% Test lists:filter/2, lists:partition/2.
 filter_partition(Config) when is_list(Config) ->
     F = fun(I) -> I rem 2 =:= 0 end,