1 files changed, 45 insertions, 0 deletions
diff --git a/src/lqueue.erl b/src/lqueue.erl
new file mode 100644
index 0000000000..8bbd52d9fc
--- /dev/null
+++ b/src/lqueue.erl
@@ -0,0 +1,45 @@
+-module(lqueue).
+
+-compile([export_all]).
+
+-define(QUEUE, queue).
+
+new() -> {0, ?QUEUE:new()}.
+
+is_empty({0, _Q}) ->
+    true;
+is_empty(_) ->
+    false.
+
+in(V, {L, Q}) -> {L+1, ?QUEUE:in(V, Q)}.
+in_r(V, {L, Q}) -> {L+1, ?QUEUE:in_r(V, Q)}.
+
+out({0, _Q} = Q) ->
+    {empty, Q};
+out({L, Q}) ->
+    {Result, Q1} = ?QUEUE:out(Q),
+    {Result, {L-1, Q1}}.
+
+out_r({0, _Q} = Q) ->
+    {empty, Q};
+out_r({L, Q}) ->
+    {Result, Q1} = ?QUEUE:out_r(Q),
+    {Result, {L-1, Q1}}.
+
+join({L1, Q1}, {L2, Q2}) ->
+    {L1 + L2, ?QUEUE:join(Q1, Q2)}.
+
+to_list({_L, Q}) ->
+    ?QUEUE:to_list(Q).
+
+from_list(L) ->
+    {length(L), ?QUEUE:from_list(L)}.
+
+queue_fold(Fun, Init, Q) ->
+    case out(Q) of
+        {empty, _Q}      -> Init;
+        {{value, V}, Q1} -> queue_fold(Fun, Fun(V, Init), Q1)
+    end.
+
+len({L, _Q}) ->
+    L.