19 lines
601 B
Text
19 lines
601 B
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: Leonardo de Moura
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-/
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prelude
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import Init.Control.Lift
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import Init.Data.String.Basic
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universes u v
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class MonadFail (m : Type u → Type v) :=
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(fail {} : ∀ {a}, String → m a)
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def matchFailed {α : Type u} {m : Type u → Type v} [MonadFail m] : m α :=
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MonadFail.fail "match failed"
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instance monadFailLift (m n : Type u → Type v) [HasMonadLift m n] [MonadFail m] [Monad n] : MonadFail n :=
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{ fail := fun α s => monadLift (MonadFail.fail s : m α) }
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