diff --git a/src/Data/Syntax/Assignment/Table/Array.hs b/src/Data/Syntax/Assignment/Table/Array.hs
index a482858de..12ec64c48 100644
--- a/src/Data/Syntax/Assignment/Table/Array.hs
+++ b/src/Data/Syntax/Assignment/Table/Array.hs
@@ -1,11 +1,16 @@
 module Data.Syntax.Assignment.Table.Array
 ( Table(tableAddresses)
 , singleton
+, fromListWith
 ) where
 
+import Control.Arrow ((&&&))
 import Data.Array
 import Data.Foldable (toList)
 import Data.Functor.Classes
+import Data.List.NonEmpty (NonEmpty(..))
+import Data.Semigroup (Max(..), Min(..), sconcat)
+import GHC.Stack
 
 data Table i a = Table { tableAddresses :: [i], tableBranches :: Array i (Maybe a) }
   deriving (Foldable, Functor, Traversable)
@@ -13,6 +18,13 @@ data Table i a = Table { tableAddresses :: [i], tableBranches :: Array i (Maybe
 singleton :: Ix i => i -> a -> Table i a
 singleton i a = Table [i] (listArray (i, i) [Just a])
 
+fromListWith :: (HasCallStack, Ix i) => (a -> a -> a) -> [(i, a)] -> Table i a
+fromListWith _ [] = error "fromList: empty list of associations"
+fromListWith with assocs@(a:as) = Table (fst <$> assocs) (accumArray merge Nothing (getMin mn, getMax mx) assocs)
+  where (mn, mx) = sconcat ((Min &&& Max) . fst <$> a:|as)
+        merge Nothing b = Just b
+        merge (Just a) b = Just (with a b)
+
 
 instance (Ix i, Show i) => Show1 (Table i) where
   liftShowsPrec spA slA d Table{..} = showsBinaryWith showsPrec (const (liftShowList spA slA)) "Table" d tableAddresses (tableAddresses >>= \ addr -> (,) addr <$> toList (tableBranches ! addr))