46 lines
1.2 KiB
Text
46 lines
1.2 KiB
Text
/-
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Copyright (c) 2017 Microsoft Corporation. All rights reserved.
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Released under Apache 2.0 license as described in the file LICENSE.
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Authors: Sebastian Ullrich
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The Reader monad transformer for passing immutable State.
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-/
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prelude
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import Init.Control.Basic
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import Init.Control.Id
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import Init.Control.Except
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universes u v w
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namespace ReaderT
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section
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variables {ρ : Type u} {m : Type u → Type v} {α : Type u}
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@[inline] protected def orElse [Alternative m] {α : Type u} (x₁ x₂ : ReaderT ρ m α) : ReaderT ρ m α :=
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fun s => x₁ s <|> x₂ s
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@[inline] protected def failure [Alternative m] {α : Type u} : ReaderT ρ m α :=
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fun s => failure
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end
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section
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variables {ρ : Type u} {m : Type u → Type v} [Monad m] {α β : Type u}
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instance [Alternative m] : Alternative (ReaderT ρ m) := {
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failure := ReaderT.failure,
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orElse := ReaderT.orElse
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}
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end
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end ReaderT
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instance (ρ : Type u) (m : Type u → Type v) : MonadControl m (ReaderT ρ m) := {
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stM := id,
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liftWith := fun f ctx => f fun x => x ctx,
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restoreM := fun x ctx => x,
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}
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instance ReaderT.tryFinally {m : Type u → Type v} {ρ : Type u} [MonadFinally m] [Monad m] : MonadFinally (ReaderT ρ m) := {
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tryFinally' := fun x h ctx => tryFinally' (x ctx) (fun a? => h a? ctx)
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}
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