175661b6c3
This PR reorganizes the monad hierarchy for symbolic computation in Lean. ## Motivation We want a clean layering where: 1. A foundational monad (`SymM`) provides maximally shared terms and structural/syntactic `isDefEq` 2. `GrindM` builds on this foundation, adding E-graphs, congruence closure, and decision procedures 3. Symbolic execution / VCGen uses `GrindM` directly without introducing a third monad ## Changes The core symbolic computation layer still lives in `Lean.Meta.Sym`. This monad (`SymM`) provides: - Maximally shared terms with pointer-based equality - Structural/syntactic `isDefEq` and matching (no reduction, predictable cost) - Monotonic local contexts (no `revert` or `clear`), enabling O(1) metavariable validation - Efficient `intro`, `apply`, and `simp` implementations The name "Sym" reflects that this is infrastructure for symbolic computation: symbolic simulation, verification condition generation, and decision procedures. ### Updated hierarchy ``` Lean.Meta.Sym -- SymM: shared terms, syntactic isDefEq, intro, apply, simp Lean.Meta.Grind -- GrindM: E-graphs, congruence closure (extends SymM) ``` Symbolic execution is a usage pattern of `GrindM` operating on `Grind.Goal`, not a separate monad. This keeps the API surface minimal: users learn two monads, and VCGen is "how you use `GrindM`" (for users that want to use `grind`) rather than a third abstraction to understand.
23 lines
565 B
Text
23 lines
565 B
Text
import Lean.Meta.Sym
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open Lean Meta Sym Internal
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def tst1 : SymM Unit := do
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let x1 ← mkBVarS 0
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let x2 ← mkBVarS 1
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let t1 ← mkAppS (← mkAppS (← mkConstS `f) x1) x2
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let t2 ← mkForallS `x BinderInfo.default (← mkConstS `Nat) t1
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IO.println (← liftLooseBVarsS t1 0 1)
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IO.println (← liftLooseBVarsS t2 0 1)
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let t3 ← lowerLooseBVarsS (← liftLooseBVarsS t2 0 1) 1 1
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IO.println t3
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assert! t2 == t3
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assert! isSameExpr t2 t3
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/--
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info: f #1 #2
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forall (x : Nat), f x #1
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forall (x : Nat), f x #0
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-/
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#guard_msgs in
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#eval SymM.run tst1
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