如何解决我们可以禁止不符合条件的论点吗?
我想部分派生输入为从属列表的函数。
deriveP
出错,因为长度为EucAppend fk (pk ::: lk)
的长度并不总是n,但是I
总是期望长度为P的列表。
这是由于lastk
和firstk
的定义。
要解决此问题,lastk
和firstk
必须仅返回Euc k
,而不返回Euc n
。
我想禁止在k <= n
和lastk
中n和k不符合firstk
的论点。
我不知道该怎么做。请告诉我。
这是R的从属列表。
Require Import Coq.Reals.Reals.
Require Import Coquelicot.Coquelicot.
Inductive Euc:nat -> Type:=
|RO : Euc 0
|Rn : forall {n:nat},R -> Euc n -> Euc (S n).
Notation "[ ]" := RO.
Notation "[ r1,..,r2 ]" := (Rn r1 .. ( Rn r2 RO ) .. ).
Infix ":::" := Rn (at level 60,right associativity).
基本列表操作。
Definition head {n} (v : Euc (S n)) : R :=
match v with
| x ::: _ => x
end.
Definition tail {n} (v : Euc (S n)) : Euc n :=
match v with
| _ ::: v => v
end.
(* extract the last element *)
Fixpoint last {n} : Euc (S n) -> R :=
match n with
| 0%nat => fun v => head v
| S n => fun v => last (tail v)
end.
(* eliminate last element from list *)
Fixpoint but_last {n} : Euc (S n) -> Euc n :=
match n with
| 0%nat => fun _ => []
| S n => fun v => head v ::: but_last (tail v)
end.
(* do the opposite of cons *)
Fixpoint snoc {n} (v : Euc n) (x : R) : Euc (S n) :=
match v with
| [] => [x]
| y ::: v => y ::: snoc v x
end.
(* extract last k elements *)
Fixpoint lastk k : forall n,Euc n -> Euc (Nat.min k n) :=
match k with
| 0%nat => fun _ _ => []
| S k' => fun n =>
match n return Euc n -> Euc (Nat.min (S k') n) with
| 0%nat => fun _ => []
| S n' => fun v =>
snoc (lastk k' _ (but_last v)) (last v)
end
end.
(* extract first k elements *)
Fixpoint firstk k :forall n,Euc n -> Euc (Nat.min k n) :=
match k with
| 0%nat => fun _ _ => []
| S k' => fun n =>
match n return Euc n -> Euc (Nat.min (S k') n) with
| 0%nat => fun _ => []
| S n' => fun v => (head v) ::: firstk k' _ (tail v)
end
end.
(* extract nth element *)
(* 0 origine *)
Fixpoint EucNth (k:nat) :forall n,Euc (S n) -> R:=
match k with
| 0%nat => fun _ e => head e
| S k' => fun n =>
match n return Euc (S n) -> R with
| 0%nat => fun e => head e
| S n' => fun v => EucNth k' n' (tail v)
end
end.
Fixpoint EucAppend {n m} (e:Euc n) (f:Euc m) :Euc (n+m):=
match e with
|[] => f
|e' ::: es => e' ::: (EucAppend es f)
end.
deriveP
部分派生功能。错误所在的地方是I (EucAppend fk (pk ::: lk))
。
Definition deriveP {n A} (k:nat) (I:Euc n -> Euc A) (p :Euc n) :=
let fk := firstk k P p in
let lk := lastk (P-(k+1)) P p in
(Derive (fun pk => I (EucAppend fk (pk ::: lk)) )) (EucNth k (P-1) p).
解决方法
您可以如上所述处理订单关系。我的建议是避免在定义中使用证明(这会使证明更加复杂),例如:
Fixpoint lastk k n : Euc n -> k < n -> Euc k :=
match n with
|0 => fun _ (H : k < 0) => False_rect _ (Lt.lt_n_O _ H)
|S n => match k with
|S m => fun v H => snoc (lastk (but_last v) (le_S_n _ _ H)) (last v)
|0 => fun _ H => []
end
end.
Fixpoint firstk k n : Euc n -> k < n -> Euc k :=
match n with
|0 => fun _ (H : k < 0) => False_rect _ (Lt.lt_n_O _ H)
|S n => match k with
|S m => fun v H => (head v) ::: firstk (tail v) (le_S_n _ _ H)
|0 => fun _ H => []
end
end.
该定义是透明的,这使得在使用k n作为归纳点后易于证明。 vectodef库可与Fin types(有限序列)一起使用。您可以采取一种变通方法以使其轻松地提取定义:
Fixpoint of_nat {n} (x : t n) : nat :=
match x with
|@F1 _ => 0
|@FS _ y => S (of_nat y)
end.
Fixpoint lastk n (H : t n) (v : Euc n) : Euc (of_nat H) :=
match H as t in (t n0) return (Euc n0 -> Euc (of_nat t)) with
| @F1 n0 => fun=> [ ]
| @FS n0 H1 =>
fun H2 : Euc (S n0) => snoc (lastk H1 (but_last H2)) (last H2)
end v.
Theorem of_nat_eq : forall y k (H : k < y),of_nat (of_nat_lt H) = k.
intros y k.
elim/@nat_double_ind : y/k.
intros;inversion H.
intros; auto.
intros; simply.
by rewrite -> (H (Lt.lt_S_n _ _ H0)).
Qed.
Definition last_leb n k (v : Euc n) : k < n -> Euc k.
intros.
rewrite <- (of_nat_eq H).
exact (@lastk _ (of_nat_lt H) v).
Show Proof.
Defined.
但是...,正如我所提到的,这在术语中有证明。
我认为您可能需要对deriveP的另一种证明,但我不知道Derive的定义,请考虑至少指定类型定义。
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