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diff --git a/users/aspen/xanthous/src/Xanthous/Util/Comonad.hs b/users/aspen/xanthous/src/Xanthous/Util/Comonad.hs
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+--------------------------------------------------------------------------------
+module Xanthous.Util.Comonad
+  ( -- * Store comonad utils
+    replace
+  , current
+  ) where
+--------------------------------------------------------------------------------
+import Xanthous.Prelude
+--------------------------------------------------------------------------------
+import Control.Comonad.Store.Class
+--------------------------------------------------------------------------------
+
+-- | Replace the current position of a store comonad with a new value by
+-- comparing positions
+replace :: (Eq i, ComonadStore i w) => w a -> a -> w a
+replace w x = w =>> \w' -> if pos w' == pos w then x else extract w'
+{-# INLINE replace #-}
+
+-- | Lens into the current position of a store comonad.
+--
+--     current = lens extract replace
+current :: (Eq i, ComonadStore i w) => Lens' (w a) a
+current = lens extract replace
+{-# INLINE current #-}