feat: add src/Init/Data/Nat/Linear.lean

This commit is contained in:
Leonardo de Moura 2022-02-24 10:56:52 -08:00
parent 43c2169f78
commit 05be43455a
4 changed files with 96 additions and 308 deletions

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@ -10,3 +10,4 @@ import Init.Data.Nat.Gcd
import Init.Data.Nat.Bitwise
import Init.Data.Nat.Control
import Init.Data.Nat.Log2
import Init.Data.Nat.Linear

View file

@ -568,6 +568,23 @@ theorem le_sub_of_add_le {a b c : Nat} (h : a + b ≤ c) : a ≤ c - b := by
| zero => rfl
| succ n ih => simp [ih, Nat.sub_succ]
protected theorem sub_self_add (n m : Nat) : n - (n + m) = 0 := by
show (n + 0) - (n + m) = 0
rw [Nat.add_sub_add_left, Nat.zero_sub]
protected theorem sub_eq_zero_of_le {n m : Nat} (h : n ≤ m) : n - m = 0 := by
match le.dest h with
| ⟨k, hk⟩ => rw [← hk, Nat.sub_self_add]
theorem sub.elim {motive : Nat → Prop}
(x y : Nat)
(h₁ : y ≤ x → (k : Nat) → x = y + k → motive k)
(h₂ : x < y → motive 0)
: motive (x - y) := by
cases Nat.lt_or_ge x y with
| inl hlt => rw [Nat.sub_eq_zero_of_le (Nat.le_of_lt hlt)]; exact h₂ hlt
| inr hle => exact h₁ hle (x - y) (Nat.add_sub_of_le hle).symm
theorem mul_pred_left (n m : Nat) : pred n * m = n * m - m := by
cases n with
| zero => simp

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@ -1,12 +1,24 @@
/-
Copyright (c) 2022 Microsoft Corporation. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Leonardo de Moura
-/
prelude
import Init.Coe
import Init.Classical
import Init.SimpLemmas
import Init.Data.Nat.Basic
import Init.Data.List.Basic
namespace Nat.Linear
/--!
Helper definitions and theorems for constructing linear arithmetic proofs.
-/
abbrev Var := Nat
structure Context where
vars : List Nat
private def List.getIdx : List α → Nat → αα
| [], i, u => u
| a::as, 0, u => a
| a::as, i+1, u => getIdx as i u
abbrev Context := List Nat
/--
When encoding polynomials. We use `fixedVar` for encoding numerals.
@ -14,7 +26,12 @@ private def List.getIdx : List α → Nat → αα
def fixedVar := 100000000 -- Any big number should work here
def Var.denote (ctx : Context) (v : Var) : Nat :=
if v = fixedVar then 1 else ctx.vars.getIdx v 0
if v = fixedVar then 1 else go ctx v
where
go : List Nat → Nat → Nat
| [], i => 0
| a::as, 0 => a
| _::as, i+1 => go as i
inductive Expr where
| num (v : Nat)
@ -22,7 +39,7 @@ inductive Expr where
| add (a b : Expr)
| mulL (k : Nat) (a : Expr)
| mulR (a : Expr) (k : Nat)
deriving Inhabited, Repr
deriving Inhabited
def Expr.denote (ctx : Context) : Expr → Nat
| Expr.add a b => Nat.add (denote ctx a) (denote ctx b)
@ -99,7 +116,9 @@ def Poly.isNum? (p : Poly) : Option Nat :=
| _ => none
def Poly.isZero (p : Poly) : Bool :=
p = []
match p with
| [] => true
| _ => false
def Poly.isNonZero (p : Poly) : Bool :=
match p with
@ -190,7 +209,6 @@ def Certificate.denote (ctx : Context) (c : Certificate) : Prop :=
| (_, c)::hs => c.denote ctx → denote ctx hs
attribute [local simp] Nat.add_comm Nat.add_assoc Nat.add_left_comm Nat.right_distrib Nat.left_distrib Nat.mul_assoc Nat.mul_comm
attribute [local simp] Poly.denote Expr.denote Poly.insertSorted Poly.sort Poly.sort.go Poly.fuse Poly.cancelAux
attribute [local simp] Poly.mul Poly.mul.go
@ -302,7 +320,7 @@ theorem Poly.of_denote_eq_cancelAux (ctx : Context) (fuel : Nat) (m₁ m₂ r₁
| succ fuel ih =>
simp at h
split at h <;> simp <;> try assumption
rename_i k₁ v₁ m₁ k₂ v₂ m₂
rename_i k₁ v₁ m₁ k₂ v₂ m₂ h
by_cases hltv : v₁ < v₂ <;> simp [hltv] at h
. have ih := ih (h := h); simp [denote_eq] at ih ⊢; assumption
. by_cases hgtv : v₁ > v₂ <;> simp [hgtv] at h
@ -381,7 +399,7 @@ theorem Poly.of_denote_le_cancelAux (ctx : Context) (fuel : Nat) (m₁ m₂ r₁
| succ fuel ih =>
simp at h
split at h <;> simp <;> try assumption
rename_i k₁ v₁ m₁ k₂ v₂ m₂
rename_i k₁ v₁ m₁ k₂ v₂ m₂ h
by_cases hltv : v₁ < v₂ <;> simp [hltv] at h
. have ih := ih (h := h); simp [denote_le] at ih ⊢; assumption
. by_cases hgtv : v₁ > v₂ <;> simp [hgtv] at h
@ -504,7 +522,9 @@ theorem Poly.isNum?_eq_some (ctx : Context) {p : Poly} {k : Nat} : p.isNum? = so
def Poly.of_isZero (ctx : Context) {p : Poly} (h : isZero p = true) : p.denote ctx = 0 := by
simp [isZero] at h
simp [h]
split at h
. simp
. contradiction
def Poly.of_isNonZero (ctx : Context) {p : Poly} (h : isNonZero p = true) : p.denote ctx > 0 := by
match p with
@ -572,49 +592,4 @@ theorem Certificate.of_combine_isUnsat (ctx : Context) (cs : Certificate) (h : c
have h := PolyCnstr.eq_false_of_isUnsat ctx h
of_combine ctx cs (fun h' => Eq.mp h h')
example (x₁ x₂ x₃ : Nat) : (x₁ + x₂) + (x₂ + x₃) = x₃ + 2*x₂ + x₁ :=
Expr.eq_of_toNormPoly { vars := [x₁, x₂, x₃] }
(Expr.add (Expr.add (Expr.var 0) (Expr.var 1)) (Expr.add (Expr.var 1) (Expr.var 2)))
(Expr.add (Expr.add (Expr.var 2) (Expr.mulL 2 (Expr.var 1))) (Expr.var 0))
rfl
example (x₁ x₂ x₃ : Nat) : ((x₁ + x₂) + (x₂ + x₃) = x₃ + x₂) = (x₁ + x₂ = 0) :=
Expr.of_cancel_eq { vars := [x₁, x₂, x₃] }
(Expr.add (Expr.add (Expr.var 0) (Expr.var 1)) (Expr.add (Expr.var 1) (Expr.var 2)))
(Expr.add (Expr.var 2) (Expr.var 1))
(Expr.add (Expr.var 0) (Expr.var 1))
(Expr.num 0)
rfl
example (x₁ x₂ x₃ : Nat) : ((x₁ + x₂) + (x₂ + x₃) ≤ x₃ + x₂) = (x₁ + x₂ ≤ 0) :=
Expr.of_cancel_le { vars := [x₁, x₂, x₃] }
(Expr.add (Expr.add (Expr.var 0) (Expr.var 1)) (Expr.add (Expr.var 1) (Expr.var 2)))
(Expr.add (Expr.var 2) (Expr.var 1))
(Expr.add (Expr.var 0) (Expr.var 1))
(Expr.num 0)
rfl
example (x₁ x₂ x₃ : Nat) : ((x₁ + x₂) + (x₂ + x₃) < x₃ + x₂) = (x₁ + x₂ < 0) :=
Expr.of_cancel_lt { vars := [x₁, x₂, x₃] }
(Expr.add (Expr.add (Expr.var 0) (Expr.var 1)) (Expr.add (Expr.var 1) (Expr.var 2)))
(Expr.add (Expr.var 2) (Expr.var 1))
(Expr.add (Expr.var 0) (Expr.var 1))
(Expr.num 0)
rfl
example (x₁ x₂ : Nat) : x₁ + 2 ≤ 3*x₂ → 4*x₂ ≤ 3 + x₁ → 3 ≤ 2*x₂ → False :=
Certificate.of_combine_isUnsat { vars := [x₁, x₂] }
[ (1, { eq := false, lhs := Expr.add (Expr.var 0) (Expr.num 2), rhs := Expr.mulL 3 (Expr.var 1) }),
(1, { eq := false, lhs := Expr.mulL 4 (Expr.var 1), rhs := Expr.add (Expr.num 3) (Expr.var 0) }),
(0, { eq := false, lhs := Expr.num 3, rhs := Expr.mulL 2 (Expr.var 1) }) ]
rfl
example (x : Nat) (xs : List Nat) : (sizeOf x < 1 + (1 + sizeOf x + sizeOf xs)) = True :=
ExprCnstr.eq_true_of_isValid { vars := [sizeOf x, sizeOf xs] }
{ eq := false, lhs := Expr.inc (Expr.var 0), rhs := Expr.add (Expr.num 1) (Expr.add (Expr.add (Expr.num 1) (Expr.var 0)) (Expr.var 1)) }
rfl
example (x : Nat) (xs : List Nat) : (1 + (1 + sizeOf x + sizeOf xs) < sizeOf x) = False :=
ExprCnstr.eq_false_of_isUnsat { vars := [sizeOf x, sizeOf xs] }
{ eq := false, lhs := Expr.inc <| Expr.add (Expr.num 1) (Expr.add (Expr.add (Expr.num 1) (Expr.var 0)) (Expr.var 1)), rhs := Expr.var 0 }
rfl
end Nat.Linear

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@ -1,253 +1,48 @@
abbrev Var := Nat
inductive Expr where
| num (v : Nat)
| var (i : Var)
| add (a b : Expr)
| mulL (k : Nat) (a : Expr)
| mulR (a : Expr) (k : Nat)
deriving Inhabited, Repr
structure Context where
vars : List Nat
def List.getIdx : List α → Var → αα
| [], i, u => u
| a::as, 0, u => a
| a::as, i+1, u => getIdx as i u
def Var.denote (ctx : Context) (v : Var) : Nat :=
ctx.vars.getIdx v 0
def Expr.denote (ctx : Context) : Expr → Nat
| Expr.add a b => Nat.add (denote ctx a) (denote ctx b)
| Expr.num k => k
| Expr.var v => v.denote ctx
| Expr.mulL k e => k * denote ctx e
| Expr.mulR e k => denote ctx e * k
abbrev Monomials := List (Nat × Var)
def Monomials.denote (ctx : Context) (m : Monomials) : Nat :=
match m with
| [] => 0
| (k, v) :: m => k * v.denote ctx + denote ctx m
def Monomials.addM (m : Monomials) (k : Nat) (v : Var) : Monomials :=
match m with
| [] => [(k, v)]
| (k', v') :: m => if v = v' then (k' + k, v) :: m else (k', v') :: addM m k v
attribute [local simp] Nat.add_comm Nat.add_assoc Nat.add_left_comm Nat.right_distrib Nat.left_distrib Nat.mul_assoc Nat.mul_comm
@[simp] theorem Monomials.denote_addM (ctx : Context) (m : Monomials) (k : Nat) (v : Var) : (m.addM k v).denote ctx = m.denote ctx + k * v.denote ctx := by
induction m with
| nil => simp [denote]
| cons kv m ih => cases kv with | _ k' v' =>
by_cases h : v = v'
. simp [h, denote, addM]
. simp [h, denote, addM, ih]
def Monomials.add (m₁ m₂ : Monomials) : Monomials :=
match m₂ with
| [] => m₁
| (k, v) :: m₂ => add (m₁.addM k v) m₂
@[simp] theorem Monomials.denote_add (ctx : Context) (m₁ m₂ : Monomials) : (m₁.add m₂).denote ctx = m₁.denote ctx + m₂.denote ctx := by
induction m₂ generalizing m₁ with
| nil => simp [add, denote]
| cons kv m₂ ih => cases kv with | _ k v =>
simp [add, denote, ih]
def Monomials.mul (k : Nat) (m : Monomials) : Monomials :=
if k = 0 then
[]
else
go m
where
go : Monomials → Monomials
| [] => []
| (k', v) :: m => (k*k', v) :: go m
@[simp] theorem Monomials.denote_mul (ctx : Context) (k : Nat) (m : Monomials) : (m.mul k).denote ctx = k * m.denote ctx := by
simp [mul]
by_cases h : k = 0
. simp [denote, h]
. simp [denote, h]
induction m with
| nil => simp [mul.go, denote]
| cons kv m ih => cases kv with | _ k' v => simp [mul.go, denote, ih]
def Monomials.insertSorted (k : Nat) (v : Var) (m : Monomials) : Monomials :=
match m with
| [] => [(k, v)]
| (k', v') :: m => if v < v' then (k, v) :: (k', v') :: m else (k', v') :: insertSorted k v m
@[simp] theorem Monomials.denote_insertSorted (ctx : Context) (k : Nat) (v : Var) (m : Monomials) : (m.insertSorted k v).denote ctx = m.denote ctx + k * v.denote ctx := by
induction m with
| nil => simp [insertSorted, denote]
| cons kv m ih => cases kv with | _ k' v' => by_cases h : v < v' <;> simp [h, insertSorted, denote, ih]
def Monomials.sort (m : Monomials) : Monomials :=
let rec go (m : Monomials) (r : Monomials) : Monomials :=
match m with
| [] => r
| (k, v) :: m => go m (r.insertSorted k v)
go m []
@[simp] theorem Monomials.denote_sort_go (ctx : Context) (m : Monomials) (r : Monomials) : (sort.go m r).denote ctx = m.denote ctx + r.denote ctx := by
induction m generalizing r with
| nil => simp [sort.go, denote]; done
| cons kv m ih => cases kv with | _ k v => simp [sort.go, denote, ih]
@[simp] theorem Monomials.denote_sort (ctx : Context) (m : Monomials) : m.sort.denote ctx = m.denote ctx := by
simp [sort, denote]
@[simp] theorem Monomials.denote_append (ctx : Context) (m₁ m₂ : Monomials) : (m₁ ++ m₂).denote ctx = m₁.denote ctx + m₂.denote ctx := by
match m₁ with
| [] => simp [denote]
| (k, v) :: m₁ => simp [denote, denote_append ctx m₁ m₂]
@[simp] theorem Monomials.denote_cons (ctx : Context) (k : Nat) (v : Var) (m : Monomials) : denote ctx ((k, v) :: m) = k * v.denote ctx + m.denote ctx := by
match m with
| [] => simp [denote]
| _ :: m => simp [denote, denote_cons ctx k v m]
@[simp] theorem Monomials.denote_reverseAux (ctx : Context) (m₁ m₂ : Monomials) : denote ctx (List.reverseAux m₁ m₂) = denote ctx (m₁ ++ m₂) := by
match m₁ with
| [] => simp [denote, List.reverseAux]
| (k, v) :: m₁ => simp [denote, List.reverseAux, denote_reverseAux ctx m₁]
@[simp] theorem Monomials.denote_reverse (ctx : Context) (m : Monomials) : denote ctx (List.reverse m) = denote ctx m := by
simp [List.reverse]
def Monomials.cancelAux (fuel : Nat) (m₁ m₂ r₁ r₂ : Monomials) : Monomials × Monomials :=
match fuel with
| 0 => (r₁.reverse ++ m₁, r₂.reverse ++ m₂)
| fuel + 1 =>
match m₁, m₂ with
| m₁, [] => (r₁.reverse ++ m₁, r₂.reverse)
| [], m₂ => (r₁.reverse, r₂.reverse ++ m₂)
| (k₁, v₁) :: m₁, (k₂, v₂) :: m₂ =>
if v₁ < v₂ then
cancelAux fuel m₁ ((k₂, v₂) :: m₂) ((k₁, v₁) :: r₁) r₂
else if v₁ > v₂ then
cancelAux fuel ((k₁, v₁) :: m₁) m₂ r₁ ((k₂, v₂) :: r₂)
else if k₁ < k₂ then
cancelAux fuel m₁ m₂ r₁ ((k₂ - k₁, v₁) :: r₂)
else if k₁ > k₂ then
cancelAux fuel m₁ m₂ ((k₁ - k₂, v₁) :: r₁) r₂
else
cancelAux fuel m₁ m₂ r₁ r₂
def Monomials.denote_eq (ctx : Context) (mp : Monomials × Monomials) : Prop := mp.1.denote ctx = mp.2.denote ctx
-- TODO : cleanup proof
theorem Monomials.denote_cancelAux (ctx : Context) (fuel : Nat) (m₁ m₂ r₁ r₂ : Monomials)
(h : denote_eq ctx (r₁.reverse ++ m₁, r₂.reverse ++ m₂)) : denote_eq ctx (cancelAux fuel m₁ m₂ r₁ r₂) := by
induction fuel generalizing m₁ m₂ r₁ r₂ with
| zero => assumption
| succ fuel ih =>
simp [cancelAux]
split
. simp_all
. simp_all
. rename_i k₁ v₁ m₁ k₂ v₂ m₂
by_cases hltv : v₁ < v₂
. simp [hltv]; apply ih; simp [denote_eq, denote] at h |-; assumption
. by_cases hgtv : v₁ > v₂
. simp [hltv, hgtv]; apply ih; simp [denote_eq, denote] at h |-; assumption
. simp [hltv, hgtv]
have heqv : v₁ = v₂ := Nat.le_antisymm (Nat.ge_of_not_lt hgtv) (Nat.ge_of_not_lt hltv)
subst heqv
by_cases hltk : k₁ < k₂
. simp [hltk]; apply ih; simp [denote_eq, denote] at h |-
rw [Nat.mul_sub_right_distrib, ← Nat.add_assoc, ← Nat.add_sub_assoc]
apply Eq.symm
apply Nat.sub_eq_of_eq_add
simp [h]
exact Nat.mul_le_mul_right _ (Nat.le_of_lt hltk)
. by_cases hgtk : k₁ > k₂
. simp [hltk, hgtk]
apply ih
simp [denote_eq, denote] at h |-
rw [Nat.mul_sub_right_distrib, ← Nat.add_assoc, ← Nat.add_sub_assoc]
apply Nat.sub_eq_of_eq_add
simp [h]
exact Nat.mul_le_mul_right _ (Nat.le_of_lt hgtk)
. simp [hltk, hgtk]
have heqk : k₁ = k₂ := Nat.le_antisymm (Nat.ge_of_not_lt hgtk) (Nat.ge_of_not_lt hltk)
subst heqk
apply ih
simp [denote_eq, denote] at h |-
rw [← Nat.add_assoc, ← Nat.add_assoc] at h
exact Nat.add_right_cancel h
def Monomials.cancel (m₁ m₂ : Monomials) : Monomials × Monomials :=
cancelAux (m₁.length + m₂.length) m₁ m₂ [] []
theorem Monomials.denote_cancel (ctx : Context) (m₁ m₂ : Monomials) (h : denote_eq ctx (m₁, m₂)) : denote_eq ctx (cancel m₁ m₂) := by
simp [cancel]
apply denote_cancelAux
simp [h]
structure Poly where
m : Monomials := []
k : Nat := 0
deriving Repr
def Poly.denote (ctx : Context) (p : Poly) : Nat :=
p.m.denote ctx + p.k
def Poly.addK (p : Poly) (k : Nat) : Poly :=
{ p with k := p.k + k }
def Poly.addM (p : Poly) (k : Nat) (v : Var) : Poly :=
{ p with m := p.m.addM k v }
@[simp] theorem Poly.denote_addM (ctx : Context) (p : Poly) (k : Nat) (v : Var) : (p.addM k v).denote ctx = p.denote ctx + k * v.denote ctx := by
simp [denote, addM]
def Poly.add (p q : Poly) : Poly :=
{ m := p.m.add q.m, k := p.k + q.k }
@[simp] theorem Poly.denote_add (ctx : Context) (p q : Poly) : (p.add q).denote ctx = p.denote ctx + q.denote ctx := by
simp [add, denote]
def Poly.mul (k : Nat) (p : Poly) : Poly :=
{ p with m := p.m.mul k, k := p.k * k }
@[simp] theorem Poly.denote_mul (ctx : Context) (k : Nat) (p : Poly) : (p.mul k).denote ctx = k * p.denote ctx := by
simp [denote, mul]
def Poly.sort (p : Poly) : Poly :=
{ p with m := p.m.sort }
@[simp] theorem Poly.denote_sort (ctx : Context) (p : Poly) : p.sort.denote ctx = p.denote ctx := by
simp [denote, sort]
def Expr.toPoly : Expr → Poly
| Expr.num k => { k }
| Expr.var i => { m := [(1, i)] }
| Expr.add a b => a.toPoly.add b.toPoly
| Expr.mulL k a => a.toPoly.mul k
| Expr.mulR a k => a.toPoly.mul k
@[simp] theorem Expr.denote_toPoly (ctx : Context) (e : Expr) : e.toPoly.denote ctx = e.denote ctx := by
induction e with
| num k => simp [denote, toPoly, Poly.denote, Monomials.denote]
| var i => simp [denote, toPoly, Poly.denote, Monomials.denote]
| add a b iha ihb => simp [denote, toPoly, iha, ihb]; done
| mulL k a ih => simp [denote, toPoly, ih]; done
| mulR k a ih => simp [denote, toPoly, ih]; done
theorem Expr.eq_of_toPoly_sort_eq (ctx : Context) (a b : Expr) (h : a.toPoly.sort = b.toPoly.sort) : a.denote ctx = b.denote ctx := by
have h := congrArg (Poly.denote ctx) h
simp at h
assumption
open Nat.Linear
example (x₁ x₂ x₃ : Nat) : (x₁ + x₂) + (x₂ + x₃) = x₃ + 2*x₂ + x₁ :=
Expr.eq_of_toPoly_sort_eq { vars := [x₁, x₂, x₃] }
Expr.eq_of_toNormPoly [x₁, x₂, x₃]
(Expr.add (Expr.add (Expr.var 0) (Expr.var 1)) (Expr.add (Expr.var 1) (Expr.var 2)))
(Expr.add (Expr.add (Expr.var 2) (Expr.mulL 2 (Expr.var 1))) (Expr.var 0))
rfl
example (x₁ x₂ x₃ : Nat) : ((x₁ + x₂) + (x₂ + x₃) = x₃ + x₂) = (x₁ + x₂ = 0) :=
Expr.of_cancel_eq [x₁, x₂, x₃]
(Expr.add (Expr.add (Expr.var 0) (Expr.var 1)) (Expr.add (Expr.var 1) (Expr.var 2)))
(Expr.add (Expr.var 2) (Expr.var 1))
(Expr.add (Expr.var 0) (Expr.var 1))
(Expr.num 0)
rfl
example (x₁ x₂ x₃ : Nat) : ((x₁ + x₂) + (x₂ + x₃) ≤ x₃ + x₂) = (x₁ + x₂ ≤ 0) :=
Expr.of_cancel_le [x₁, x₂, x₃]
(Expr.add (Expr.add (Expr.var 0) (Expr.var 1)) (Expr.add (Expr.var 1) (Expr.var 2)))
(Expr.add (Expr.var 2) (Expr.var 1))
(Expr.add (Expr.var 0) (Expr.var 1))
(Expr.num 0)
rfl
example (x₁ x₂ x₃ : Nat) : ((x₁ + x₂) + (x₂ + x₃) < x₃ + x₂) = (x₁ + x₂ < 0) :=
Expr.of_cancel_lt [x₁, x₂, x₃]
(Expr.add (Expr.add (Expr.var 0) (Expr.var 1)) (Expr.add (Expr.var 1) (Expr.var 2)))
(Expr.add (Expr.var 2) (Expr.var 1))
(Expr.add (Expr.var 0) (Expr.var 1))
(Expr.num 0)
rfl
example (x₁ x₂ : Nat) : x₁ + 2 ≤ 3*x₂ → 4*x₂ ≤ 3 + x₁ → 3 ≤ 2*x₂ → False :=
Certificate.of_combine_isUnsat [x₁, x₂]
[ (1, { eq := false, lhs := Expr.add (Expr.var 0) (Expr.num 2), rhs := Expr.mulL 3 (Expr.var 1) }),
(1, { eq := false, lhs := Expr.mulL 4 (Expr.var 1), rhs := Expr.add (Expr.num 3) (Expr.var 0) }),
(0, { eq := false, lhs := Expr.num 3, rhs := Expr.mulL 2 (Expr.var 1) }) ]
rfl
example (x : Nat) (xs : List Nat) : (sizeOf x < 1 + (1 + sizeOf x + sizeOf xs)) = True :=
ExprCnstr.eq_true_of_isValid [sizeOf x, sizeOf xs]
{ eq := false, lhs := Expr.inc (Expr.var 0), rhs := Expr.add (Expr.num 1) (Expr.add (Expr.add (Expr.num 1) (Expr.var 0)) (Expr.var 1)) }
rfl
example (x : Nat) (xs : List Nat) : (1 + (1 + sizeOf x + sizeOf xs) < sizeOf x) = False :=
ExprCnstr.eq_false_of_isUnsat [sizeOf x, sizeOf xs]
{ eq := false, lhs := Expr.inc <| Expr.add (Expr.num 1) (Expr.add (Expr.add (Expr.num 1) (Expr.var 0)) (Expr.var 1)), rhs := Expr.var 0 }
rfl