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Project-declaredLean 4.32.0 · mathlib@81a5d257

Simulate Q triple preserves invariant

OracleComp.ProgramLogic.StdDo.simulateQ_triple_preserves_invariant

Plain-language statement

Generic simulation triple: if every handler call handler t preserves an invariant I on the simulation state, then simulateQ handler oa preserves I for any oa : OracleComp spec α. The invariant-only form (same I as pre- and post-condition, independent of return value) is the most common case; stronger per-call specs can be derived by instantiat...

Exact Lean statement

theorem simulateQ_triple_preserves_invariant {σ α : Type}
    (handler : QueryImpl spec (StateT σ (OracleComp spec)))
    (I : σ → Prop)
    (hhandler : ∀ t : spec.Domain, Std.Do.Triple (handler t)
      (spred(fun s => ⌜I s⌝))
      (⇓ _ s' => ⌜I s'⌝))
    (oa : OracleComp spec α) :
    Std.Do.Triple
      (simulateQ handler oa : StateT σ (OracleComp spec) α)
      (spred(fun s => ⌜I s⌝))
      (⇓ _ s' => ⌜I s'⌝)

Formal artifact

Lean source

Canonical source
Full Lean sourceLean 4
theorem simulateQ_triple_preserves_invariant {σ α : Type}    (handler : QueryImpl spec (StateT σ (OracleComp spec)))    (I : σ  Prop)    (hhandler :  t : spec.Domain, Std.Do.Triple (handler t)      (spred(fun s => ⌜I s⌝))      (⇓ _ s' => ⌜I s'⌝))    (oa : OracleComp spec α) :    Std.Do.Triple      (simulateQ handler oa : StateT σ (OracleComp spec) α)      (spred(fun s => ⌜I s⌝))      (⇓ _ s' => ⌜I s'⌝) := by  -- A pure `Std.Do`-level proof via `Triple.pure` / `Triple.bind` is the  -- structurally right thing, but consistently times out on `isDefEq` in  -- the `query_bind` step (verified up to 1M heartbeats with several  -- variations: explicit `R`, explicit `Q`, stripping `liftM` via  -- `simulateQ_bind` + `simulateQ_query` + `id_map`). The cost appears to  -- be in `(wp x).mono` reduction inside `Triple.bind` for the  -- `StateT σ (OracleComp spec)` instance; this is plausibly a `Std.Do`  -- upstream issue worth reporting.  --  -- For now, bail out once to the support layer and induct directly on  -- `oa`. Downstream consumers stay in the `Std.Do` world.  rw [triple_stateT_iff_forall_support]  induction oa using OracleComp.inductionOn with  | pure x =>    intro s hs a s' hmem    simp only [simulateQ_pure, StateT.run_pure, support_pure, Set.mem_singleton_iff,      Prod.mk.injEq] at hmem    obtain _, hseq := hmem    exact hseq ▸ hs  | query_bind t oa ih =>    intro s hs a s' hmem    simp only [simulateQ_query_bind, OracleQuery.input_query,      StateT.run_bind, support_bind, Set.mem_iUnion] at hmem    obtain ⟨⟨u, s₁, hmem₁, hmem₂ := hmem    have hhand := hhandler t    rw [triple_stateT_iff_forall_support] at hhand    exact ih u s₁ (hhand s hs u s₁ hmem₁) a s' hmem₂
Project
VCVio
License
Apache-2.0
Commit
2ceb2d825ee3
Source
VCVio/ProgramLogic/Unary/HandlerSpecs.lean:161-198

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