5 files changed, 27 insertions, 1 deletions
diff --git a/lib/ur/basis.urs b/lib/ur/basis.urs
index c893e65d..be13c684 100644
--- a/lib/ur/basis.urs
+++ b/lib/ur/basis.urs
@@ -1019,6 +1019,8 @@ val checkMime : string -> option mimeType
 val returnBlob : t ::: Type -> blob -> mimeType -> transaction t
 val blobSize : blob -> int
 val textBlob : string -> blob
+val textOfBlob : blob -> option string
+(* Returns [Some] exactly when the blob contains no zero bytes. *)
 
 type postBody
 val postType : postBody -> string
diff --git a/lib/ur/listPair.ur b/lib/ur/listPair.ur
index 94b92872..c5e70708 100644
--- a/lib/ur/listPair.ur
+++ b/lib/ur/listPair.ur
@@ -40,7 +40,21 @@ fun mp [a] [b] [c] (f : a -> b -> c) =
             case (ls1, ls2) of
                 ([], []) => []
               | (x1 :: ls1, x2 :: ls2) => f x1 x2 :: map' ls1 ls2
-              | _ => error <xml>ListPair.map2: Unequal list lengths</xml>
+              | _ => error <xml>ListPair.mp: Unequal list lengths</xml>
     in
         map'
     end
+
+fun mapM [m] (_ : monad m) [a] [b] [c] (f : a -> b -> m c) =
+    let
+        fun mapM' ls1 ls2 =
+            case (ls1, ls2) of
+                ([], []) => return []
+              | (x1 :: ls1, x2 :: ls2) =>
+                y <- f x1 x2;
+                ls <- mapM' ls1 ls2;
+                return (y :: ls)
+              | _ => error <xml>ListPair.mapM: Unequal list lengths</xml>
+    in
+        mapM'
+    end
diff --git a/lib/ur/listPair.urs b/lib/ur/listPair.urs
index b473e226..9efff405 100644
--- a/lib/ur/listPair.urs
+++ b/lib/ur/listPair.urs
@@ -8,3 +8,6 @@ val all : a ::: Type -> b ::: Type -> (a -> b -> bool) -> list a -> list b -> bo
 
 val mp : a ::: Type -> b ::: Type -> c ::: Type
          -> (a -> b -> c) -> list a -> list b -> list c
+
+val mapM : m ::: (Type -> Type) -> monad m -> a ::: Type -> b ::: Type -> c ::: Type
+         -> (a -> b -> m c) -> list a -> list b -> m (list c)
diff --git a/lib/ur/option.ur b/lib/ur/option.ur
index baa08466..dd186161 100644
--- a/lib/ur/option.ur
+++ b/lib/ur/option.ur
@@ -59,3 +59,8 @@ fun unsafeGet [a] (o : option a) =
     case o of
         None   => error <xml>Option.unsafeGet: encountered None</xml>
       | Some v => v
+
+fun mapM [m] (_ : monad m) [a] [b] (f : a -> m b) (x : t a) : m (t b) =
+    case x of
+        None => return None
+      | Some y => z <- f y; return (Some z)
diff --git a/lib/ur/option.urs b/lib/ur/option.urs
index c30c40e7..705c0313 100644
--- a/lib/ur/option.urs
+++ b/lib/ur/option.urs
@@ -14,3 +14,5 @@ val bind : a ::: Type -> b ::: Type -> (a -> option b) -> t a -> t b
 
 val get : a ::: Type -> a -> option a -> a
 val unsafeGet : a ::: Type -> option a -> a
+
+val mapM : m ::: (Type -> Type) -> monad m -> a ::: Type -> b ::: Type -> (a -> m b) -> t a -> m (t b)