Lean migration: Phase 7 (Sign + Constant analyses, executable)

- Spa.Showable: port of Showable.agda (quoted strings, map format) for
  output parity
- Spa.Analysis.Utils: eval_combine₂
- Spa.Lattice.AboveBelow.le_cases: order of the flat lattice by cases
- Spa.Analysis.Sign / Spa.Analysis.Constant: the four monotonicity
  POSTULATES from the Agda files are now proved theorems (via le_cases);
  interpretations, evaluator validity, analyze_correct per analysis
- Main + lake exe spa: runs both analyses on the Agda test program;
  constant analysis folds unknown=0, sign analysis gives unknown=⊤

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
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2026-06-09 20:52:08 -07:00
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/-
Port of `Analysis/Constant.agda`.
Correspondence:
showable, ≡-equiv, ≡-Decidable- ↦ (mathlib/derived instances)
ConstLattice (AboveBelow ) ↦ ConstLattice
AB.Plain (+ 0) ↦ constFixedHeight
plus, minus ↦ plus, minus
plus-Monoˡ/ʳ, minus-Monoˡ/ʳ (postulates in Agda!)
↦ plus_mono_left/right, minus_mono_left/right
— now actually proved, via AboveBelow.le_cases
plus-Mono₂, minus-Mono₂ ↦ plus_mono₂, minus_mono₂
⟦_⟧ᶜ ↦ interpConst
⟦⟧ᶜ-respects-≈ᶜ ↦ (trivial with `=`)
⟦⟧ᶜ-⊔ᶜ-, ⟦⟧ᶜ-⊓ᶜ-∧ ↦ interpConst_sup, interpConst_inf
s₁≢s₂⇒¬s₁∧s₂ ↦ interpConst_mk_disjoint
latticeInterpretationᶜ ↦ constInterpretation
WithProg.eval, eval-Monoʳ ↦ ConstAnalysis.eval, eval_mono
ConstEval ↦ ConstAnalysis.exprEvaluator
plus-valid, minus-valid ↦ plus_valid, minus_valid
eval-valid, ConstEvalValid ↦ eval_valid
output ↦ ConstAnalysis.output
analyze-correct ↦ ConstAnalysis.analyze_correct
-/
import Spa.Analysis.Forward
import Spa.Analysis.Utils
import Spa.Showable
namespace Spa
abbrev ConstLattice : Type := AboveBelow
/-- Agda: `AB.Plain (+ 0)`'s `fixedHeight`. -/
def constFixedHeight : FixedHeight ConstLattice 2 :=
AboveBelow.plainFixedHeight (0 : )
namespace ConstAnalysis
open AboveBelow in
/-- Agda: `plus`. -/
def plus : ConstLattice ConstLattice ConstLattice
| bot, _ => bot
| _, bot => bot
| top, _ => top
| _, top => top
| mk z₁, mk z₂ => mk (z₁ + z₂)
open AboveBelow in
/-- Agda: `minus`. -/
def minus : ConstLattice ConstLattice ConstLattice
| bot, _ => bot
| _, bot => bot
| top, _ => top
| _, top => top
| mk z₁, mk z₂ => mk (z₁ - z₂)
/-- Agda: `plus-Monoˡ` — a postulate there, a theorem here. -/
theorem plus_mono_left (s₂ : ConstLattice) : Monotone (plus · s₂) := by
intro a b h
rcases AboveBelow.le_cases h with rfl | rfl | rfl
· rcases s₂ with _ | _ | y <;> rcases b with _ | _ | x <;>
simp only [plus] <;>
first
| exact le_refl _
| exact AboveBelow.le_top' _
| exact AboveBelow.bot_le' _
· rcases s₂ with _ | _ | y <;> rcases a with _ | _ | x <;>
simp only [plus] <;>
first
| exact le_refl _
| exact AboveBelow.le_top' _
· exact le_refl _
/-- Agda: `plus-Monoʳ` — a postulate there, a theorem here. -/
theorem plus_mono_right (s₁ : ConstLattice) : Monotone (plus s₁) := by
intro a b h
rcases AboveBelow.le_cases h with rfl | rfl | rfl
· rcases s₁ with _ | _ | x <;> rcases b with _ | _ | y <;>
simp only [plus] <;>
first
| exact le_refl _
| exact AboveBelow.le_top' _
| exact AboveBelow.bot_le' _
· rcases s₁ with _ | _ | x <;> rcases a with _ | _ | y <;>
simp only [plus] <;>
first
| exact le_refl _
| exact AboveBelow.le_top' _
· exact le_refl _
/-- Agda: `plus-Mono₂`. -/
theorem plus_mono₂ : Monotone₂ plus :=
plus_mono_left, plus_mono_right
/-- Agda: `minus-Monoˡ` — a postulate there, a theorem here. -/
theorem minus_mono_left (s₂ : ConstLattice) : Monotone (minus · s₂) := by
intro a b h
rcases AboveBelow.le_cases h with rfl | rfl | rfl
· rcases s₂ with _ | _ | y <;> rcases b with _ | _ | x <;>
simp only [minus] <;>
first
| exact le_refl _
| exact AboveBelow.le_top' _
| exact AboveBelow.bot_le' _
· rcases s₂ with _ | _ | y <;> rcases a with _ | _ | x <;>
simp only [minus] <;>
first
| exact le_refl _
| exact AboveBelow.le_top' _
· exact le_refl _
/-- Agda: `minus-Monoʳ` — a postulate there, a theorem here. -/
theorem minus_mono_right (s₁ : ConstLattice) : Monotone (minus s₁) := by
intro a b h
rcases AboveBelow.le_cases h with rfl | rfl | rfl
· rcases s₁ with _ | _ | x <;> rcases b with _ | _ | y <;>
simp only [minus] <;>
first
| exact le_refl _
| exact AboveBelow.le_top' _
| exact AboveBelow.bot_le' _
· rcases s₁ with _ | _ | x <;> rcases a with _ | _ | y <;>
simp only [minus] <;>
first
| exact le_refl _
| exact AboveBelow.le_top' _
· exact le_refl _
/-- Agda: `minus-Mono₂`. -/
theorem minus_mono₂ : Monotone₂ minus :=
minus_mono_left, minus_mono_right
/-- Agda: `⟦_⟧ᶜ`. -/
def interpConst : ConstLattice Value Prop
| .bot, _ => False
| .top, _ => True
| .mk z, v => v = .int z
/-- Agda: `s₁≢s₂⇒¬s₁∧s₂`. -/
theorem interpConst_mk_disjoint {z₁ z₂ : } (hne : z₁ z₂) {v : Value} :
¬(interpConst (.mk z₁) v interpConst (.mk z₂) v) := by
rintro h₁, h₂
rw [h₁] at h₂
injection h₂ with hz
exact hne hz
/-- Agda: `⟦⟧ᶜ-⊔ᶜ-`. -/
theorem interpConst_sup {s₁ s₂ : ConstLattice} (v : Value)
(h : interpConst s₁ v interpConst s₂ v) : interpConst (s₁ s₂) v := by
rcases s₁ with _ | _ | z₁
· rcases h with h | h
· exact h.elim
· rw [AboveBelow.bot_sup]
exact h
· exact trivial
· rcases s₂ with _ | _ | z₂
· rcases h with h | h
· rw [AboveBelow.sup_bot]
exact h
· exact h.elim
· rw [AboveBelow.sup_top]
exact trivial
· by_cases hz : z₁ = z₂
· subst hz
rw [AboveBelow.mk_sup_mk, if_pos rfl]
rcases h with h | h <;> exact h
· rw [AboveBelow.mk_sup_mk, if_neg hz]
exact trivial
/-- Agda: `⟦⟧ᶜ-⊓ᶜ-∧`. -/
theorem interpConst_inf {s₁ s₂ : ConstLattice} (v : Value)
(h : interpConst s₁ v interpConst s₂ v) : interpConst (s₁ s₂) v := by
rcases s₁ with _ | _ | z₁
· exact h.1
· rw [AboveBelow.top_inf]
exact h.2
· rcases s₂ with _ | _ | z₂
· exact h.2
· rw [AboveBelow.inf_top]
exact h.1
· by_cases hz : z₁ = z₂
· subst hz
rw [AboveBelow.mk_inf_mk, if_pos rfl]
exact h.1
· exact absurd h (interpConst_mk_disjoint hz)
/-- Agda: `latticeInterpretationᶜ`. -/
def constInterpretation : LatticeInterpretation ConstLattice where
interp := interpConst
interp_sup := fun {l₁ l₂} v h => interpConst_sup (s₁ := l₁) (s₂ := l₂) v h
interp_inf := fun {l₁ l₂} v h => interpConst_inf (s₁ := l₁) (s₂ := l₂) v h
variable (prog : Program)
/-- Agda: `WithProg.eval`. -/
def eval : Expr VariableValues ConstLattice prog ConstLattice
| .add e₁ e₂, vs => plus (eval e₁ vs) (eval e₂ vs)
| .sub e₁ e₂, vs => minus (eval e₁ vs) (eval e₂ vs)
| .var k, vs =>
if h : FiniteMap.MemKey k vs then (FiniteMap.locate h).1 else .top
| .num n, _ => .mk n
/-- Agda: `WithProg.eval-Monoʳ`. -/
theorem eval_mono (e : Expr) : Monotone (eval prog e) := by
induction e with
| add e₁ e₂ ih₁ ih₂ =>
intro vs₁ vs₂ h
exact eval_combine₂ plus_mono₂ (ih₁ h) (ih₂ h)
| sub e₁ e₂ ih₁ ih₂ =>
intro vs₁ vs₂ h
exact eval_combine₂ minus_mono₂ (ih₁ h) (ih₂ h)
| var k =>
intro vs₁ vs₂ h
simp only [eval]
by_cases hk : k prog.vars
· rw [dif_pos (FiniteMap.memKey_iff.mpr hk),
dif_pos (FiniteMap.memKey_iff.mpr hk)]
exact FiniteMap.le_of_mem_mem prog.vars_nodup h
(FiniteMap.locate _).2 (FiniteMap.locate _).2
· rw [dif_neg (fun hm => hk (FiniteMap.memKey_iff.mp hm)),
dif_neg (fun hm => hk (FiniteMap.memKey_iff.mp hm))]
| num n =>
intro vs₁ vs₂ _
exact le_refl _
/-- Agda: the `ConstEval` instance. -/
def exprEvaluator : ExprEvaluator ConstLattice prog :=
eval prog, eval_mono prog
/-- Agda: `WithProg.result`/`output`. -/
def output : String :=
show' (result constFixedHeight (exprEvaluator prog).toStmtEvaluator)
/-- Agda: `plus-valid`. -/
theorem plus_valid {g₁ g₂ : ConstLattice} {z₁ z₂ : }
(h₁ : interpConst g₁ (.int z₁)) (h₂ : interpConst g₂ (.int z₂)) :
interpConst (plus g₁ g₂) (.int (z₁ + z₂)) := by
rcases g₁ with _ | _ | c₁
· exact h₁.elim
· rcases g₂ with _ | _ | c₂
· exact h₂.elim
· exact trivial
· exact trivial
· rcases g₂ with _ | _ | c₂
· exact h₂.elim
· exact trivial
· injection h₁ with hz₁
injection h₂ with hz₂
show Value.int (z₁ + z₂) = Value.int (c₁ + c₂)
rw [hz₁, hz₂]
/-- Agda: `minus-valid`. -/
theorem minus_valid {g₁ g₂ : ConstLattice} {z₁ z₂ : }
(h₁ : interpConst g₁ (.int z₁)) (h₂ : interpConst g₂ (.int z₂)) :
interpConst (minus g₁ g₂) (.int (z₁ - z₂)) := by
rcases g₁ with _ | _ | c₁
· exact h₁.elim
· rcases g₂ with _ | _ | c₂
· exact h₂.elim
· exact trivial
· exact trivial
· rcases g₂ with _ | _ | c₂
· exact h₂.elim
· exact trivial
· injection h₁ with hz₁
injection h₂ with hz₂
show Value.int (z₁ - z₂) = Value.int (c₁ - c₂)
rw [hz₁, hz₂]
/-- Agda: `eval-valid` / `ConstEvalValid`. -/
theorem eval_valid :
IsValidExprEvaluator (exprEvaluator prog) constInterpretation := by
intro vs ρ e v hev
induction hev with
| num n =>
intro _
show interpConst (eval prog (.num n) vs) (.int n)
rfl
| var x v hxv =>
intro hvs
show interpConst (eval prog (.var x) vs) v
simp only [eval]
by_cases hk : FiniteMap.MemKey x vs
· rw [dif_pos hk]
exact hvs _ _ (FiniteMap.locate hk).2 _ hxv
· rw [dif_neg hk]
exact trivial
| add e₁ e₂ z₁ z₂ _ _ ih₁ ih₂ =>
intro hvs
have h₁ : interpConst (eval prog e₁ vs) (.int z₁) := ih₁ hvs
have h₂ : interpConst (eval prog e₂ vs) (.int z₂) := ih₂ hvs
show interpConst (eval prog (.add e₁ e₂) vs) (.int (z₁ + z₂))
exact plus_valid h₁ h₂
| sub e₁ e₂ z₁ z₂ _ _ ih₁ ih₂ =>
intro hvs
have h₁ : interpConst (eval prog e₁ vs) (.int z₁) := ih₁ hvs
have h₂ : interpConst (eval prog e₂ vs) (.int z₂) := ih₂ hvs
show interpConst (eval prog (.sub e₁ e₂) vs) (.int (z₁ - z₂))
exact minus_valid h₁ h₂
/-- Agda: `WithProg.analyze-correct`. -/
theorem analyze_correct {ρ : Env} (hrun : EvalStmt [] prog.rootStmt ρ) :
interpV constInterpretation
(variablesAt prog.finalState
(result constFixedHeight (exprEvaluator prog).toStmtEvaluator)) ρ :=
Spa.analyze_correct constFixedHeight
((exprEvaluator prog).toStmtEvaluator_valid (eval_valid prog)) hrun
end ConstAnalysis
end Spa