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Idris-dev/effects/Effect/Select.idr
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1module Effect.Select
3import Effects
5data Selection : Effect where
6 Select : List a -> Selection () () a
8instance Handler Selection Maybe where
9 handle _ (Select xs) k = tryAll xs where
10 tryAll [] = Nothing
11 tryAll (x :: xs) = case k () x of
12 Nothing => tryAll xs
13 Just v => Just v
15instance Handler Selection List where
16 handle r (Select xs) k = concatMap (k r) xs
18SELECT : EFFECT
19SELECT = MkEff () Selection
21select : List a -> Eff m [SELECT] a
22select xs = Select xs