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authorGravatar Adam Chlipala <adam@chlipala.net>2018-12-31 14:48:16 -0500
committerGravatar Adam Chlipala <adam@chlipala.net>2018-12-31 14:48:16 -0500
commit4ada57be570bfbe18137c5b37ed5e0d327de82db (patch)
tree94781877bfd974d64ba9fc4d6fd223e4125c29b9 /lib/ur
parent7340651c636cb3fc1fde05cb4ae0db95e6716f2c (diff)
ListPair.mapM
Diffstat (limited to 'lib/ur')
-rw-r--r--lib/ur/listPair.ur16
-rw-r--r--lib/ur/listPair.urs3
2 files changed, 18 insertions, 1 deletions
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)