From 42f761814d055971894f61926f193d4ce48e0934 Mon Sep 17 00:00:00 2001
From: Timothee Cour <timothee.cour2@gmail.com>
Date: Wed, 17 Feb 2021 10:06:44 -0800
Subject: [PATCH 1/2] make std/lists usable with ptr instead of ref

---
 lib/pure/collections/lists.nim | 18 +++++++++++++++---
 1 file changed, 15 insertions(+), 3 deletions(-)

diff --git a/lib/pure/collections/lists.nim b/lib/pure/collections/lists.nim
index e1c3808b20492..03eb77b38a8c7 100644
--- a/lib/pure/collections/lists.nim
+++ b/lib/pure/collections/lists.nim
@@ -81,6 +81,10 @@ type
     value*: T
   SinglyLinkedNode*[T] = ref SinglyLinkedNodeObj[T]
 
+  SinglyLinkedNodePtr*[T] = object
+    next*: ptr SinglyLinkedNodePtr[T]
+    value*: T
+
   SinglyLinkedList*[T] = object ## \
     ## A singly linked list.
     ##
@@ -89,6 +93,10 @@ type
     head*: <//>(SinglyLinkedNode[T])
     tail* {.cursor.}: SinglyLinkedNode[T]
 
+  SinglyLinkedListPtr*[T] = object
+    head*: ptr SinglyLinkedNodePtr[T]
+    tail*: ptr SinglyLinkedNodePtr[T]
+
   DoublyLinkedList*[T] = object ## \
     ## A doubly linked list.
     ##
@@ -112,7 +120,7 @@ type
     ## a new empty ring.
     head*: DoublyLinkedNode[T]
 
-  SomeLinkedList*[T] = SinglyLinkedList[T] | DoublyLinkedList[T]
+  SomeLinkedList*[T] = SinglyLinkedList[T] | DoublyLinkedList[T] | SinglyLinkedListPtr[T]
 
   SomeLinkedRing*[T] = SinglyLinkedRing[T] | DoublyLinkedRing[T]
 
@@ -126,6 +134,9 @@ proc initSinglyLinkedList*[T](): SinglyLinkedList[T] =
     var a = initSinglyLinkedList[int]()
   discard
 
+proc initSinglyLinkedListPtr*[T](): SinglyLinkedListPtr[T] =
+  discard
+
 proc initDoublyLinkedList*[T](): DoublyLinkedList[T] =
   ## Creates a new doubly linked list that is empty.
   runnableExamples:
@@ -399,8 +410,9 @@ proc prependMoved*[T: SomeLinkedList](a, b: var T) {.since: (1, 5, 1).} =
     (b, a) = (a, b)
   else: swap a, b
 
-proc add*[T](L: var SinglyLinkedList[T],
-             n: SinglyLinkedNode[T]) {.inline.} =
+# proc add*[T](L: var (SinglyLinkedList[T] | SinglyLinkedListPtr[T]), n: type(L.tail)) {.inline.} = # xxx make this work
+proc add*[T](L: var (SinglyLinkedList[T] | SinglyLinkedListPtr[T]),
+             n: SinglyLinkedNode[T] | ptr SinglyLinkedNodePtr[T]) {.inline.} =
   ## Appends (adds to the end) a node `n` to `L`. Efficiency: O(1).
   ##
   ## See also:

From 5a704885fdd4b6ddd0c227d5475019eaf7dc79b0 Mon Sep 17 00:00:00 2001
From: Timothee Cour <timothee.cour2@gmail.com>
Date: Wed, 17 Feb 2021 10:09:00 -0800
Subject: [PATCH 2/2] add test

---
 tests/stdlib/tlists.nim | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/tests/stdlib/tlists.nim b/tests/stdlib/tlists.nim
index 2d3165c9c8fbe..89dd278b99af2 100644
--- a/tests/stdlib/tlists.nim
+++ b/tests/stdlib/tlists.nim
@@ -231,3 +231,11 @@ block remove: # return value check
   doAssert l.toSeq == [1]
   doAssert l.remove(l.head) == true
   doAssert l.toSeq == []
+
+block: # SinglyLinkedNodePtr, etc
+  var list = initSinglyLinkedListPtr[int]()
+  var nodes: array[4, SinglyLinkedNodePtr[int]]
+  for i,n in mpairs(nodes):
+    n.value = i
+    list.add n.addr
+  doAssert toSeq(list) == [0,1,2,3]