116 lines
3.8 KiB
Text
116 lines
3.8 KiB
Text
/-
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Copyright (c) 2016 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.monad init.meta.exceptional init.meta.format
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/-
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Remark: we use a function that produces a format object as the exception information.
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Motivation: the formatting object may be big, and we may create it on demand.
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Remark: We use base_tactic_result to define base_tactic (a monad that combines the state an exceptional monads).
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We "merge" them for performance reasons.
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-/
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inductive base_tactic_result (S : Type) (A : Type) :=
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| success : A → S → base_tactic_result S A
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| exception : (options → format) → S → base_tactic_result S A
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section
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open base_tactic_result
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variables {S A : Type}
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variables [has_to_string A]
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protected meta_definition base_tactic_result.to_string : base_tactic_result S A → string
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| (success a s) := to_string a
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| (exception A e s) := "Exception: " + to_string (e options.mk)
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protected meta_definition base_tactic_result.has_to_string [instance] : has_to_string (base_tactic_result S A) :=
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has_to_string.mk base_tactic_result.to_string
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end
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meta_definition base_tactic [reducible] (S : Type) (A : Type) :=
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S → base_tactic_result S A
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namespace base_tactic
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variables {S A B : Type}
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open base_tactic_result
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inline protected meta_definition fmap (f : A → B) (t : base_tactic S A) : base_tactic S B :=
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λ s, base_tactic_result.cases_on (t s)
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(λ a s', success (f a) s')
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(λ e s', exception B e s')
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inline protected meta_definition bind (t₁ : base_tactic S A) (t₂ : A → base_tactic S B) : base_tactic S B :=
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λ s : S, base_tactic_result.cases_on (t₁ s)
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(λ a s', t₂ a s')
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(λ e s', exception B e s')
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inline protected meta_definition return (a : A) : base_tactic S A :=
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λ s, success a s
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end base_tactic
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meta_definition base_tactic.is_monad [instance] (S : Type) : monad (base_tactic S) :=
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monad.mk (@base_tactic.fmap S) (@base_tactic.return S) (@base_tactic.bind S)
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namespace tactic
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variables {S A : Type}
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open base_tactic_result
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meta_definition fail {A B : Type} [has_to_format B] (msg : B) : base_tactic S A :=
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λ s, exception A (λ u, to_fmt msg) s
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meta_definition failed : base_tactic S A :=
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fail "failed"
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meta_definition try (t : base_tactic S A) : base_tactic S unit :=
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λ s, base_tactic_result.cases_on (t s)
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(λ a, success ())
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(λ e s', success () s)
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meta_definition or_else (t₁ t₂ : base_tactic S A) : base_tactic S A :=
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λ s, base_tactic_result.cases_on (t₁ s)
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success
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(λ e₁ s', base_tactic_result.cases_on (t₂ s)
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success
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(exception A))
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infix `<|>`:1 := or_else
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meta_definition skip : base_tactic S unit :=
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success ()
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open list
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meta_definition repeat : list A → (A → base_tactic S unit) → base_tactic S unit
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| [] fn := skip
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| (e::es) fn := do fn e, repeat es fn
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open nat
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/- (repeat n t): repeat the given tactic at most n times or until t fails -/
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meta_definition repeat_at_most : nat → base_tactic S unit → base_tactic S unit
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| 0 t := skip
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| (succ n) t := (do t, repeat_at_most n t) <|> skip
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/- (do n t) : execute t n times -/
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meta_definition repeat_exactly : nat → base_tactic S unit → base_tactic S unit
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| 0 t := skip
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| (succ n) t := do t, repeat_exactly n t
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meta_definition returnex (e : exceptional A) : base_tactic S A :=
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λ s, match e with
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| exceptional.success a := base_tactic_result.success a s
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| exceptional.exception A f := base_tactic_result.exception A f s
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end
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/- Decorate t's exceptions with msg -/
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meta_definition decorate_ex (msg : format) (t : base_tactic S A) : base_tactic S A :=
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λ s, base_tactic_result.cases_on (t s)
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success
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(λ e, !exception (λ u, msg + format.nest 2 (format.line + e u)))
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inline meta_definition write (s' : S) : base_tactic S unit :=
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λ s, success () s'
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inline meta_definition read : base_tactic S S :=
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λ s, success s s
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end tactic
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