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Add a semigroup instance for CollSt #3

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Add a semigroup instance for CollSt #3

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8 changes: 6 additions & 2 deletions src/Control/Monad/SD/STCLang.hs
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Original file line number Diff line number Diff line change
Expand Up @@ -10,6 +10,7 @@ import Control.Monad.SD.Ohua
import Control.Monad.SD.Smap
import Data.Dynamic2
import Data.StateElement
import Data.Semigroup

import Control.DeepSeq (NFData)
import Control.Monad.State as S
Expand All @@ -19,10 +20,13 @@ data CollSt = CollSt
, signals :: [IO S]
}

instance Semigroup CollSt where
(CollSt st1 si1) <> (CollSt st2 si2) =
CollSt (st1 <> st2) (si1 <> si2)

instance Monoid CollSt where
mempty = CollSt [] []
CollSt st1 si1 `mappend` CollSt st2 si2 =
CollSt (st1 `mappend` st2) (si1 `mappend` si2)
mappend = (<>)

type STCLang a b = StateT CollSt IO (a -> OhuaM b)

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