1 files changed, 46 insertions, 0 deletions
diff --git a/lib/ur/listPair.ur b/lib/ur/listPair.ur
new file mode 100644
index 0000000..94b9287
--- /dev/null
+++ b/lib/ur/listPair.ur
@@ -0,0 +1,46 @@
+fun foldlAbort [a] [b] [c] f =
+    let
+        fun foldlAbort' acc ls1 ls2 =
+            case (ls1, ls2) of
+                ([], []) => Some acc
+              | (x1 :: ls1, x2 :: ls2) =>
+                (case f x1 x2 acc of
+                     None => None
+                   | Some acc' => foldlAbort' acc' ls1 ls2)
+              | _ => None
+    in
+        foldlAbort'
+    end
+
+fun mapX [a] [b] [ctx ::: {Unit}] f =
+    let
+        fun mapX' ls1 ls2 =
+            case (ls1, ls2) of
+                ([], []) => <xml/>
+              | (x1 :: ls1, x2 :: ls2) => <xml>{f x1 x2}{mapX' ls1 ls2}</xml>
+              | _ => error <xml>ListPair.mapX: Unequal list lengths</xml>
+    in
+        mapX'
+    end
+
+fun all [a] [b] f =
+    let
+        fun all' ls1 ls2 =
+            case (ls1, ls2) of
+                ([], []) => True
+              | (x1 :: ls1, x2 :: ls2) => f x1 x2 && all' ls1 ls2
+              | _ => False
+    in
+        all'
+    end
+
+fun mp [a] [b] [c] (f : a -> b -> c) =
+    let
+        fun map' ls1 ls2 =
+            case (ls1, ls2) of
+                ([], []) => []
+              | (x1 :: ls1, x2 :: ls2) => f x1 x2 :: map' ls1 ls2
+              | _ => error <xml>ListPair.map2: Unequal list lengths</xml>
+    in
+        map'
+    end