I have a sequence of applications in that way (f (f (fx))), being f an arbitrary function and any applications numbers sequences. I want to prove that f (xy) and (x (fy)), x = (fff ...) and y = any value, it's equal. I need that proof in the code below:
Fixpoint r_nat {A : Type} (a : nat) : A -> (A -> A) -> A :=
match a with
|S n => fun (x0 : A) (a0 : A -> A) => r_nat n (a0 x0) a0
|0 => fun (x0 : A) (_ : A -> A) => x0
end.
Theorem homomo_nat : forall {T} (f : T -> T) (h : T) (x : nat), (r_nat x (f h) f) = f ((r_nat x) h f) .
compute.
??.
Qed.
I try unfolding and refining but doesn't work.
这应该可以通过对x
的感应( f
的施加次数)来解决。
I moved the argument (x:nat)
before (h:T)
. That makes the induction hypothesis stronger - it holds for all h
. Then the proof is simply:
Theorem homomo_nat : forall {T} (f : T -> T) (x:nat) (h : T), (r_nat x (f h) f) = f ((r_nat x) h f) .
Proof.
induction x.
reflexivity.
intros. apply IHx.
Qed.
You can also "move the arguments around" with tactics to keep your original theorem if you prefer that... Start with intros; generalize dependent h.
intros; generalize dependent h.
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