Add a drop command

Add a drop command, bound to 'd', which prompts the character for an
item in their inventory, removes it from the inventory, and places it on
the ground. Along the way I had to fix a bug in the
`EntityMap.atPosition` lens, which was always appending to the existing
entities at the position on set, without removing the entities that were
already there - the rabbit hole of quickchecking the lens laws here also
lead to replacing the target of this lens with a newtype called
`VectorBag`, which ignores order (since the entitymap makes no
guarantees about order of entities at a given position).

1 files changed, 2 insertions, 1 deletions

diff --git a/src/Xanthous/Game/State.hs b/src/Xanthous/Game/State.hs
index 3b401d366d10..d8a0f0b32077 100644
--- a/src/Xanthous/Game/State.hs
+++ b/src/Xanthous/Game/State.hs
@@ -80,6 +80,7 @@ import           Xanthous.Util (KnownBool(..))
 import           Xanthous.Data
 import           Xanthous.Data.EntityMap (EntityMap, EntityID)
 import           Xanthous.Data.EntityChar
+import           Xanthous.Data.VectorBag
 import           Xanthous.Orphans ()
 import           Xanthous.Game.Prompt
 import           Xanthous.Resource
@@ -185,7 +186,7 @@ type AppM = AppT (EventM Name)
 --------------------------------------------------------------------------------
 
 class Draw a where
-  drawWithNeighbors :: Neighbors (Vector SomeEntity) -> a -> Widget n
+  drawWithNeighbors :: Neighbors (VectorBag SomeEntity) -> a -> Widget n
   drawWithNeighbors = const draw
 
   draw :: a -> Widget n