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Add "choice"

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This is called asum in Haskell. I think it's appropriate for the Prelude
because I've defined it myself on a number of occasions.
This commit is contained in:
David Raymond Christiansen 2015-08-12 22:28:49 -07:00
parent 030da056bc
commit d76b58360e
1 changed files with 7 additions and 0 deletions
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7
libs/prelude/Prelude/Applicative.idr
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@ -5,6 +5,7 @@ import Builtins
import Prelude.Basics
import Prelude.Bool
import Prelude.Classes
import Prelude.Foldable
import Prelude.Functor
---- Applicative functors/Idioms
@ -48,3 +49,9 @@ guard a = if a then pure () else empty
when : Applicative f => Bool -> Lazy (f ()) -> f ()
when True f = Force f
when False f = pure ()
||| Fold using Alternative
|||
||| This is called `asum` in Haskell.
choice : (Foldable t, Alternative f) => t (f a) -> f a
choice x = foldr (<|>) empty x