List.searchM and ListPair.unzip

4 files changed, 28 insertions, 0 deletions

diff --git a/lib/ur/list.ur b/lib/ur/list.ur
index 10877420..b38097b7 100644
--- a/lib/ur/list.ur
+++ b/lib/ur/list.ur
@@ -293,6 +293,20 @@ fun search [a] [b] f =
         search'
     end
 
+fun searchM [m] (_ : monad m) [a] [b] f =
+    let
+        fun search' ls =
+            case ls of
+                [] => return None
+              | x :: ls =>
+                o <- f x;
+                case o of
+                    None => search' ls
+                  | v => return v
+    in
+        search'
+    end
+
 fun foldlM [m] (_ : monad m) [a] [b] f =
     let
         fun foldlM' acc ls =
diff --git a/lib/ur/list.urs b/lib/ur/list.urs
index c1d46022..7e3cf205 100644
--- a/lib/ur/list.urs
+++ b/lib/ur/list.urs
@@ -67,6 +67,8 @@ val findM : m ::: (Type -> Type) -> monad m -> a ::: Type -> (a -> m bool) -> t
 
 val search : a ::: Type -> b ::: Type -> (a -> option b) -> t a -> option b
 
+val searchM : m ::: (Type -> Type) -> monad m -> a ::: Type -> b ::: Type -> (a -> m (option b)) -> t a -> m (option b)
+
 val all : a ::: Type -> (a -> bool) -> t a -> bool
 
 val allM : m ::: (Type -> Type) -> monad m -> a ::: Type -> (a -> m bool) -> t a -> m bool
diff --git a/lib/ur/listPair.ur b/lib/ur/listPair.ur
index c5e70708..52c73cd8 100644
--- a/lib/ur/listPair.ur
+++ b/lib/ur/listPair.ur
@@ -58,3 +58,13 @@ fun mapM [m] (_ : monad m) [a] [b] [c] (f : a -> b -> m c) =
     in
         mapM'
     end
+
+fun unzip [a] [b] (ls : list (a * b)) : list a * list b =
+    let
+        fun unzip' ls ls1 ls2 =
+            case ls of
+                [] => (List.rev ls1, List.rev ls2)
+              | (x1, x2) :: ls => unzip' ls (x1 :: ls1) (x2 :: ls2)
+    in
+        unzip' ls [] []
+    end
diff --git a/lib/ur/listPair.urs b/lib/ur/listPair.urs
index 9efff405..91d8807d 100644
--- a/lib/ur/listPair.urs
+++ b/lib/ur/listPair.urs
@@ -11,3 +11,5 @@ val mp : a ::: Type -> b ::: Type -> c ::: Type
 
 val mapM : m ::: (Type -> Type) -> monad m -> a ::: Type -> b ::: Type -> c ::: Type
          -> (a -> b -> m c) -> list a -> list b -> m (list c)
+
+val unzip : a ::: Type -> b ::: Type -> list (a * b) -> list a * list b