Coq 如何证明转换参数的关系的可判定性?
我曾定义过一种归纳数据类型Coq 如何证明转换参数的关系的可判定性?,coq,proof,deterministic,formal-verification,partial-ordering,Coq,Proof,Deterministic,Formal Verification,Partial Ordering,我曾定义过一种归纳数据类型t,并在其上定义了一个偏序le(c.f.le\u refl,le\u trans,以及le\u antisym)。在le_C的情况下,顺序具有这种特殊性,即在归纳假设中参数的顺序被交换 正因为如此,我没有成功地证明这种排序关系是确定性的(c.f.le_dec)。有问题的子目标如下 1 subgoal t1 : t IHt1 : forall t2 : t, {le t1 t2} + {~ le t1 t2} t2 : t ________________________
t
,并在其上定义了一个偏序le
(c.f.le\u refl
,le\u trans
,以及le\u antisym
)。在le_C
的情况下,顺序具有这种特殊性,即在归纳假设中参数的顺序被交换
正因为如此,我没有成功地证明这种排序关系是确定性的(c.f.le_dec
)。有问题的子目标如下
1 subgoal
t1 : t
IHt1 : forall t2 : t, {le t1 t2} + {~ le t1 t2}
t2 : t
______________________________________(1/1)
{le (C t1) (C t2)} + {~ le (C t1) (C t2)}
归纳假设指的是let2t2
,而我需要let2t1
当我考虑这个问题时,它是有意义的,这个二元函数既不是第一个参数的原始递归函数,也不是第二个参数的原始递归函数,而是两个参数对的递归函数。我的印象是,我应该以某种方式同时对这两个论点进行归纳,但不知道如何做到这一点
我确实设法定义了一个布尔函数leb
,并用它来证明leu dec
,但从学习的角度来看,我想知道如何直接用归纳法进行证明
问题
le
的定义直接证明le_dec
(即,不首先定义等价的布尔函数)Ltac自毁事件:=
与对手重复比赛进球
|H:存在124;-124;=>析构函数H
|H:\uu/\\u124;-\ u=>自毁H
结束;替代品。
引理leu_dec_aux(t1 t2:t)(n:nat):
高度t1+高度t2
{le t1 t2}+{~le t1 t2}。
证明。
回复t1-t2。
诱导n为[|n IH];简介t1 t2h。
-破坏t1;H中的simple;欧米茄。
-破坏t1,t2。
+伊奥托使用了一种新方法。
+清楚。正确的。对映介绍。依赖诱导对映体。
应用le_规范形式,在第1页左边;替换:eauto。
+清楚。正确的。对映介绍。依赖诱导对映体。
应用le_规范形式,在第1页左边;替换:eauto。
+清楚。正确的。对映介绍。依赖诱导对映体。
应用le_规范形式_B_左相反1;自毁。奥托。
+H中的simple。
自毁(IH t1 t2);试试欧米茄。
*伊奥托使用了一种新方法。
*对。对映介绍。相反地应用le_倒装法。矛盾
+清楚。正确的。对映介绍。依赖诱导对映体。
应用le_规范形式_B_左相反1;自毁。奥托。
+清楚。正确的。对映介绍。依赖诱导对映体。
应用le_规范形式_C_左相反1;自毁。奥托。
+清楚。正确的。对映介绍。依赖诱导对映体。
应用le_规范形式_C_左相反1;自毁。奥托。
+H中的simple。
自毁(IH t2 t1);试试欧米茄。
*伊奥托使用了一种新方法。
*对。对映介绍。相反地应用le_倒装法。矛盾
Qed。
引理leu_dec'(t1 t2:t):
{le t1 t2}+{~le t1 t2}。
证明。
自毁(高度t1+高度t2);自动的。
Qed。
与您用于定义leb
功能的方法类似,您需要通过归纳元素高度来证明leu dec
:
Lemma le_dec_aux t1 t2 n : height t1 + height t2 <= n -> {le t1 t2} + {~le t1 t2}.
Proof.
revert t1 t2.
induction n as [|n IH].
(* ... *)
引理le_dec_aux t1 t2n:height t1+height t2{le t1 t2}+{~le t1 t2}。
证明。
回复t1-t2。
诱导n为[| n IH]。
(* ... *)
也就是说,我认为用布尔函数证明可判定性是完全正确的。该库广泛使用此模式,使用专门的
reflect
谓词将一般命题连接到布尔计算,而不是sumbool
类型{a}+{B}
与您用于定义leb
函数类似,您需要通过归纳元素高度来证明leu dec
:
Lemma le_dec_aux t1 t2 n : height t1 + height t2 <= n -> {le t1 t2} + {~le t1 t2}.
Proof.
revert t1 t2.
induction n as [|n IH].
(* ... *)
引理le_dec_aux t1 t2n:height t1+height t2{le t1 t2}+{~le t1 t2}。
证明。
回复t1-t2。
诱导n为[| n IH]。
(* ... *)
也就是说,我认为用布尔函数证明可判定性是完全正确的。该库广泛使用此模式,使用专门的
reflect
谓词将一般命题连接到布尔计算,而不是sumbool
类型{a}+{B}
我尝试了@Arthur建议的版本,使用了有充分根据的递归。
这确实提供了一个很好的提取
Definition rel p1 p2 := height_pair p1 < height_pair p2.
Lemma rel_wf : well_founded rel.
Proof.
apply well_founded_ltof.
Qed.
Lemma le_dec (t1 t2 : t) :
{ le t1 t2 } + { ~le t1 t2 }.
Proof.
induction t1, t2 as [t1 t2]
using (fun P => well_founded_induction_type_2 P rel_wf).
destruct t1, t2;
try (right; intros contra;
(apply le_canonical_form_A_left in contra)
|| (apply le_canonical_form_B_left in contra; destruct contra)
|| (apply le_canonical_form_C_left in contra; destruct contra);
discriminate).
- left. apply le_A.
- destruct (H t1 t2).
+ unfold rel, height_pair; simpl. omega.
+ left. apply le_B. assumption.
+ right. intros contra. apply le_inversion_B in contra. contradiction.
- destruct (H t2 t1).
+ unfold rel, height_pair; simpl. omega.
+ left. apply le_C. assumption.
+ right. intros contra. apply le_inversion_C in contra. contradiction.
Qed.
Extraction Inline well_founded_induction_type_2 Fix_F_2.
(* to have a nice extraction *)
Extraction le_dec.
我尝试了@Arthur建议的版本,使用了有充分根据的递归。 这确实提供了一个很好的提取
Definition rel p1 p2 := height_pair p1 < height_pair p2.
Lemma rel_wf : well_founded rel.
Proof.
apply well_founded_ltof.
Qed.
Lemma le_dec (t1 t2 : t) :
{ le t1 t2 } + { ~le t1 t2 }.
Proof.
induction t1, t2 as [t1 t2]
using (fun P => well_founded_induction_type_2 P rel_wf).
destruct t1, t2;
try (right; intros contra;
(apply le_canonical_form_A_left in contra)
|| (apply le_canonical_form_B_left in contra; destruct contra)
|| (apply le_canonical_form_C_left in contra; destruct contra);
discriminate).
- left. apply le_A.
- destruct (H t1 t2).
+ unfold rel, height_pair; simpl. omega.
+ left. apply le_B. assumption.
+ right. intros contra. apply le_inversion_B in contra. contradiction.
- destruct (H t2 t1).
+ unfold rel, height_pair; simpl. omega.
+ left. apply le_C. assumption.
+ right. intros contra. apply le_inversion_C in contra. contradiction.
Qed.
Extraction Inline well_founded_induction_type_2 Fix_F_2.
(* to have a nice extraction *)
Extraction le_dec.
非常感谢你!现在我可以比较布尔函数和直接证明,我觉得它们的复杂度和开销相当。我还比较了提取的OCaml代码,有趣的是,生成的代码完全相同,只是
le_dec
首先执行了高度t1+高度t2的无用计算。因此,在实际需要计算关系是否成立的情况下,布尔函数有一个优势。如果要提取该函数,最好使用有充分基础的递归()对其进行编程。您仍然需要使用终止参数使函数被接受,但它不会干扰函数的计算行为。非常感谢!现在我可以比较布尔函数和直接证明,我觉得它们的复杂度和开销相当。我还比较了提取的OCaml代码,有趣的是,生成的代码完全相同,只是le_dec
首先执行了高度t1+高度t2的无用计算。因此,在实际需要计算关系是否成立的情况下,布尔函数有一个优势。如果要提取该函数,最好使用有充分基础的递归()对其进行编程。你仍然需要使用一个小键盘
Lemma le_dec (t1 t2 : t) :
{ le t1 t2 } + { ~le t1 t2 }.
Proof.
revert t2.
induction t1; intros t2.
- destruct t2.
+ eauto using le.
+ right. intro contra. dependent induction contra.
apply le_canonical_form_A_left in contra1; subst. eauto.
+ right. intro contra. dependent induction contra.
apply le_canonical_form_A_left in contra1; subst. eauto.
- destruct t2.
+ right. intro contra. clear IHt1. dependent induction contra.
apply le_canonical_form_B_left in contra1 as [? ?]; subst. eauto.
+ destruct IHt1 with t2.
* eauto using le.
* right. intro contra. apply le_inversion_B in contra. contradiction.
+ right; intro contra. clear IHt1. dependent induction contra.
apply le_canonical_form_B_left in contra1 as [? ?]; subst. eauto.
- destruct t2.
+ right. intro contra. clear IHt1. dependent induction contra.
apply le_canonical_form_C_left in contra1 as [? ?]; subst. eauto.
+ right. intro contra. clear IHt1. dependent induction contra.
apply le_canonical_form_C_left in contra1 as [? ?]; subst. eauto.
+ destruct IHt1 with t2.
* admit. (* Wrong assumption *)
* admit. (* Wrong assumption *)
Restart.
destruct (leb (t1, t2)) eqn:Heqn.
- apply leb_to_le in Heqn. auto.
- right. intro contra. apply le_to_leb in contra.
rewrite Heqn in contra. discriminate.
Qed.
Ltac destruct_exs_conjs :=
repeat match goal with
| H : exists _, _ |- _ => destruct H
| H : _ /\ _ |- _ => destruct H
end; subst.
Lemma le_dec_aux (t1 t2 : t) (n : nat) :
height t1 + height t2 <= n ->
{le t1 t2} + {~le t1 t2}.
Proof.
revert t1 t2.
induction n as [| n IH]; intros t1 t2 H.
- destruct t1; simpl in H; omega.
- destruct t1, t2.
+ eauto using le.
+ clear. right. intro contra. dependent induction contra.
apply le_canonical_form_A_left in contra1; subst. eauto.
+ clear. right. intro contra. dependent induction contra.
apply le_canonical_form_A_left in contra1; subst. eauto.
+ clear. right. intro contra. dependent induction contra.
apply le_canonical_form_B_left in contra1; destruct_exs_conjs. eauto.
+ simpl in H.
destruct (IH t1 t2); try omega.
* eauto using le.
* right. intro contra. apply le_inversion_B in contra. contradiction.
+ clear. right. intro contra. dependent induction contra.
apply le_canonical_form_B_left in contra1; destruct_exs_conjs. eauto.
+ clear. right. intro contra. dependent induction contra.
apply le_canonical_form_C_left in contra1; destruct_exs_conjs. eauto.
+ clear. right. intro contra. dependent induction contra.
apply le_canonical_form_C_left in contra1; destruct_exs_conjs. eauto.
+ simpl in H.
destruct (IH t2 t1); try omega.
* eauto using le.
* right. intro contra. apply le_inversion_C in contra. contradiction.
Qed.
Lemma le_dec' (t1 t2 : t) :
{ le t1 t2 } + { ~le t1 t2 }.
Proof.
destruct (le_dec_aux t1 t2 (height t1 + height t2)); auto.
Qed.
Lemma le_dec_aux t1 t2 n : height t1 + height t2 <= n -> {le t1 t2} + {~le t1 t2}.
Proof.
revert t1 t2.
induction n as [|n IH].
(* ... *)
Definition rel p1 p2 := height_pair p1 < height_pair p2.
Lemma rel_wf : well_founded rel.
Proof.
apply well_founded_ltof.
Qed.
Lemma le_dec (t1 t2 : t) :
{ le t1 t2 } + { ~le t1 t2 }.
Proof.
induction t1, t2 as [t1 t2]
using (fun P => well_founded_induction_type_2 P rel_wf).
destruct t1, t2;
try (right; intros contra;
(apply le_canonical_form_A_left in contra)
|| (apply le_canonical_form_B_left in contra; destruct contra)
|| (apply le_canonical_form_C_left in contra; destruct contra);
discriminate).
- left. apply le_A.
- destruct (H t1 t2).
+ unfold rel, height_pair; simpl. omega.
+ left. apply le_B. assumption.
+ right. intros contra. apply le_inversion_B in contra. contradiction.
- destruct (H t2 t1).
+ unfold rel, height_pair; simpl. omega.
+ left. apply le_C. assumption.
+ right. intros contra. apply le_inversion_C in contra. contradiction.
Qed.
Extraction Inline well_founded_induction_type_2 Fix_F_2.
(* to have a nice extraction *)
Extraction le_dec.
Lemma le_is_eq : forall t1 t2, le t1 t2 -> t1 = t2.
Proof.
intros.
induction t1, t2 as [t1 t2]
using (fun P => well_founded_induction_type_2 P rel_wf).
destruct t1, t2;
try ((apply le_canonical_form_A_left in H)
|| (apply le_canonical_form_B_left in H; destruct H)
|| (apply le_canonical_form_C_left in H; destruct H);
discriminate).
- reflexivity.
- apply le_inversion_B in H.
apply H0 in H.
+ congruence.
+ unfold rel, height_pair. simpl. omega.
- apply le_inversion_C in H.
apply H0 in H.
+ congruence.
+ unfold rel, height_pair. simpl. omega.
Qed.