2 files changed, 8 insertions, 0 deletions
diff --git a/src/Xanthous/Data/EntityMap.hs b/src/Xanthous/Data/EntityMap.hs
index 5b5e8a063f2c..a068828a157c 100644
--- a/src/Xanthous/Data/EntityMap.hs
+++ b/src/Xanthous/Data/EntityMap.hs
@@ -110,6 +110,9 @@ instance TraversableWithIndex EntityID EntityMap where
   itraversed = byID . itraversed . rmap sequenceA . distrib
   itraverse = itraverseOf itraversed
 
+type instance Element (EntityMap a) = a
+instance MonoFoldable (EntityMap a)
+
 emptyEntityMap :: EntityMap a
 emptyEntityMap = EntityMap mempty mempty 0
 
diff --git a/src/Xanthous/Data/EntityMap/Graphics.hs b/src/Xanthous/Data/EntityMap/Graphics.hs
index 3124c6a334cc..ace5ae49e804 100644
--- a/src/Xanthous/Data/EntityMap/Graphics.hs
+++ b/src/Xanthous/Data/EntityMap/Graphics.hs
@@ -4,6 +4,7 @@ module Xanthous.Data.EntityMap.Graphics
   ( visiblePositions
   , visibleEntities
   , linesOfSight
+  , canSee
   ) where
 --------------------------------------------------------------------------------
 import Xanthous.Prelude hiding (lines)
@@ -49,3 +50,7 @@ visibleEntities pos visionRadius
   . map (\(p, es) -> over _2 (Positioned p) <$> es)
   . fold
   . linesOfSight pos visionRadius
+
+canSee :: Entity e => (e -> Bool) -> Position -> Word -> EntityMap e -> Bool
+canSee match pos radius = any match . visibleEntities pos radius
+-- ^ this might be optimizable