108 lines
5.2 KiB
Text
108 lines
5.2 KiB
Text
/-
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Copyright (c) 2020 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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import Lean.Meta.Basic
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namespace Lean
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inductive TransformStep :=
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| done (e : Expr)
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| visit (e : Expr)
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namespace Core
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/--
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Tranform the expression `input` using `pre` and `post`.
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- `pre s` is invoked before visiting the children of subterm 's'. If the result is `TransformStep.visit sNew`, then
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`sNew` is traversed by transform. If the result is `TransformStep.visit sNew`, then `s` is just replaced with `sNew`.
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In both cases, `sNew` must be definitionally equal to `s`
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- `post s` is invoked after visiting the children of subterm `s`.
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The term `s` in both `pre s` and `post s` may contain loose bound variables. So, this method is not appropriate for
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if one needs to apply operations (e.g., `whnf`, `inferType`) that do not handle loose bound variables.
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Consider using `Meta.transform` to avoid loose bound variables.
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This method is useful for applying transformations such as beta-reduction and delta-reduction.
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-/
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partial def transform {m} [Monad m] [MonadLiftT CoreM m] [MonadControlT CoreM m]
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(input : Expr)
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(pre : Expr → m TransformStep := fun e => return TransformStep.visit e)
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(post : Expr → m TransformStep := fun e => return TransformStep.done e)
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: m Expr :=
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let inst : STWorld IO.RealWorld m := ⟨⟩
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let inst : MonadLiftT (ST IO.RealWorld) m := { monadLift := fun x => liftM (m := CoreM) (liftM (m := ST IO.RealWorld) x) }
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let rec visit (e : Expr) : MonadCacheT Expr Expr m Expr :=
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checkCache e fun e => Core.withIncRecDepth do
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let rec visitPost (e : Expr) : MonadCacheT Expr Expr m Expr := do
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match (← post e) with
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| TransformStep.done e => pure e
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| TransformStep.visit e => visit e
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match (← pre e) with
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| TransformStep.done e => pure e
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| TransformStep.visit e => match e with
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| Expr.forallE _ d b _ => visitPost (e.updateForallE! (← visit d) (← visit b))
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| Expr.lam _ d b _ => visitPost (e.updateLambdaE! (← visit d) (← visit b))
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| Expr.letE _ t v b _ => visitPost (e.updateLet! (← visit t) (← visit v) (← visit b))
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| Expr.app .. => e.withApp fun f args => do visitPost (mkAppN (← visit f) (← args.mapM visit))
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| Expr.mdata _ b _ => visitPost (e.updateMData! (← visit b))
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| Expr.proj _ _ b _ => visitPost (e.updateProj! (← visit b))
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| _ => visitPost e
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visit input |>.run
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end Core
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namespace Meta
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/--
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Similar to `Core.transform`, but terms provided to `pre` and `post` do not contain loose bound variables.
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So, it is safe to use any `MetaM` method at `pre` and `post`. -/
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partial def transform {m} [Monad m] [MonadLiftT MetaM m] [MonadControlT MetaM m]
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(input : Expr)
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(pre : Expr → m TransformStep := fun e => return TransformStep.visit e)
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(post : Expr → m TransformStep := fun e => return TransformStep.done e)
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: m Expr :=
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let inst : STWorld IO.RealWorld m := ⟨⟩
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let inst : MonadLiftT (ST IO.RealWorld) m := { monadLift := fun x => liftM (m := MetaM) (liftM (m := ST IO.RealWorld) x) }
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let rec visit (e : Expr) : MonadCacheT Expr Expr m Expr :=
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checkCache e fun e => Meta.withIncRecDepth do
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let rec visitPost (e : Expr) : MonadCacheT Expr Expr m Expr := do
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match (← post e) with
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| TransformStep.done e => pure e
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| TransformStep.visit e => visit e
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let rec visitLambda (fvars : Array Expr) (e : Expr) : MonadCacheT Expr Expr m Expr := do
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match e with
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| Expr.lam n d b c =>
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withLocalDecl n c.binderInfo (← visit (d.instantiateRev fvars)) fun x =>
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visitLambda (fvars.push x) b
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| e => visitPost (← mkLambdaFVars fvars (← visit (e.instantiateRev fvars)))
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let rec visitForall (fvars : Array Expr) (e : Expr) : MonadCacheT Expr Expr m Expr := do
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match e with
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| Expr.forallE n d b c =>
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withLocalDecl n c.binderInfo (← visit (d.instantiateRev fvars)) fun x =>
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visitForall (fvars.push x) b
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| e => visitPost (← mkForallFVars fvars (← visit (e.instantiateRev fvars)))
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let rec visitLet (fvars : Array Expr) (e : Expr) : MonadCacheT Expr Expr m Expr := do
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match e with
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| Expr.letE n t v b _ =>
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withLetDecl n (← visit (t.instantiateRev fvars)) (← visit (v.instantiateRev fvars)) fun x =>
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visitLet (fvars.push x) b
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| e => visitPost (← mkLetFVars fvars (← visit (e.instantiateRev fvars)))
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let visitApp (e : Expr) : MonadCacheT Expr Expr m Expr :=
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e.withApp fun f args => do
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visitPost (mkAppN (← visit f) (← args.mapM visit))
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match (← pre e) with
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| TransformStep.done e => pure e
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| TransformStep.visit e => match e with
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| Expr.forallE .. => visitLambda #[] e
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| Expr.lam .. => visitForall #[] e
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| Expr.letE .. => visitLet #[] e
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| Expr.app .. => visitApp e
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| Expr.mdata _ b _ => visitPost (e.updateMData! (← visit b))
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| Expr.proj _ _ b _ => visitPost (e.updateProj! (← visit b))
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| _ => visitPost e
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visit input |>.run
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end Meta
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end Lean
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