49 lines
2 KiB
Text
49 lines
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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Author: Leonardo de Moura
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-/
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import Lean.Data.Occurrences
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import Lean.HeadIndex
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import Lean.Meta.Basic
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namespace Lean.Meta
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/--
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Abstract occurrences of `p` in `e`. We detect subterms equivalent to `p` using key-matching.
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That is, only perform `isDefEq` tests when the head symbol of substerm is equivalent to head symbol of `p`.
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By default, all occurrences are abstracted, but this behavior can be controlled using the `occs` parameter.
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-/
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def kabstract (e : Expr) (p : Expr) (occs : Occurrences := .all) : MetaM Expr := do
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let e ← instantiateMVars e
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if p.isFVar && occs == Occurrences.all then
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return e.abstract #[p] -- Easy case
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else
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let pHeadIdx := p.toHeadIndex
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let pNumArgs := p.headNumArgs
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let rec visit (e : Expr) (offset : Nat) : StateRefT Nat MetaM Expr := do
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let visitChildren : Unit → StateRefT Nat MetaM Expr := fun _ => do
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match e with
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| .app f a => return e.updateApp! (← visit f offset) (← visit a offset)
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| .mdata _ b => return e.updateMData! (← visit b offset)
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| .proj _ _ b => return e.updateProj! (← visit b offset)
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| .letE _ t v b _ => return e.updateLet! (← visit t offset) (← visit v offset) (← visit b (offset+1))
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| .lam _ d b _ => return e.updateLambdaE! (← visit d offset) (← visit b (offset+1))
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| .forallE _ d b _ => return e.updateForallE! (← visit d offset) (← visit b (offset+1))
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| e => return e
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if e.hasLooseBVars then
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visitChildren ()
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else if e.toHeadIndex != pHeadIdx || e.headNumArgs != pNumArgs then
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visitChildren ()
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else if (← isDefEq e p) then
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let i ← get
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set (i+1)
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if occs.contains i then
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return mkBVar offset
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else
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visitChildren ()
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else
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visitChildren ()
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visit e 0 |>.run' 1
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end Lean.Meta
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