# [isabelle] newbie question

[possible duplicate, I jumped the gun on sending the first before I was properly subscribed].
```
I'm trying to prove a simple proof related to the "reverse" proof
in the tutorial (I have the rest of the tutorial theory here
as well including lemmas app_Nil2, app_assoc, rev_app and rev_rev):

--- snip ---
revH :: "'a list => 'a list => 'a list"

primrec
"revH [] ys = ys"
"revH (x # xs) ys = revH xs (x # ys)"
...

lemma rev_revH: "revH xs ys = rev xs @ ys"
apply(induct_tac xs)
apply(auto)
done

lemma rev_rev2: "rev xs = revH xs []"
apply(induct_tac xs)
apply(auto)
done
--- snip ---

```
when I evaluate the first lemma it is able to automatically reduce the problem to the goal:
```
forall a list.
revH list ys = rev list @ ys ==>
revH list (a # ys) = rev list @ a # ys

```
To me this seems to imply that this is solved, but I guess Isabelle doesn't see it that way. I tried to strengthen the proof by saying
```"!! ys ." but that didn't seem to have any effect.  What do I need to
do here to complete this proof?

Tim Newsham
http://www.thenewsh.com/~newsham/

```

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