diff options
Diffstat (limited to 'lib/ur/listPair.ur')
-rw-r--r-- | lib/ur/listPair.ur | 16 |
1 files changed, 15 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 |