3b89739850
Note that hash_map is moved to library_dev, where the more advanced theorems on lists are available
36 lines
1.2 KiB
Text
36 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: Leonardo de Moura
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-/
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prelude
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import init.data.option.basic
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import init.meta.tactic
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universes u v
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@[inline] def option_bind {α : Type u} {β : Type v} : option α → (α → option β) → option β
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| none b := none
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| (some a) b := b a
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instance : monad option :=
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{pure := @some, bind := @option_bind,
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id_map := λ α x, option.rec rfl (λ x, rfl) x,
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pure_bind := λ α β x f, rfl,
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bind_assoc := λ α β γ x f g, option.rec rfl (λ x, rfl) x}
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def option_orelse {α : Type u} : option α → option α → option α
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| (some a) o := some a
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| none (some a) := some a
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| none none := none
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instance : alternative option :=
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{ option.monad with
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failure := @none,
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orelse := @option_orelse }
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lemma option.eq_of_eq_some {α : Type u} : Π {x y : option α}, (∀z, x = some z ↔ y = some z) → x = y
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| none none h := rfl
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| none (some z) h := option.no_confusion ((h z).2 rfl)
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| (some z) none h := option.no_confusion ((h z).1 rfl)
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| (some z) (some w) h := option.no_confusion ((h w).2 rfl) (congr_arg some)
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