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authorAspen Smith <grfn@gws.fyi>2024-02-12T03·00-0500
committerclbot <clbot@tvl.fyi>2024-02-14T19·37+0000
commit82ecd61f5c699cf3af6c4eadf47a1c52b1d696c6 (patch)
tree429c5e078528000591742ec3211bc768ae913a78 /users/aspen/xanthous/src/Xanthous/Util/Comonad.hs
parent0ba476a4266015f278f18d74094299de74a5a111 (diff)
chore(users): grfn -> aspen r/7511
Change-Id: I6c6847fac56f0a9a1a2209792e00a3aec5e672b9
Reviewed-on: https://cl.tvl.fyi/c/depot/+/10809
Autosubmit: aspen <root@gws.fyi>
Reviewed-by: sterni <sternenseemann@systemli.org>
Tested-by: BuildkiteCI
Reviewed-by: lukegb <lukegb@tvl.fyi>
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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 #-}