Hi,

OK, great, thanks! It seems that EQ_IMP_RULE is the key ... (I’ll remember 
FORALL_AND_THM too)

P. S. Just after my post, I found an ugly solution too ^_^:

GEN_ALL (MATCH_MP AND1_THM (SPEC_ALL (ONCE_REWRITE_RULE [EQ_IMP_THM] th))

—Chun

> Il giorno 22 gen 2017, alle ore 23:19, [email protected] ha 
> scritto:
> 
> Try something like GEN_ALL o #1 o EQ_IMP_RULE o SPEC_ALL.
> 
> Or following up on your rewriting approach, you might also rewrite with
> 
>  SIMP_RULE bool_ss [FORALL_AND_THM]
> 
> to move the universal quantification in over the conjunctions.  (This has the 
> issue that it might disturb other universal quantifications within the P or 
> Q…)
> 
> Michael
> 
> On 23/1/17, 09:08, "Chun Tian (binghe)" <[email protected]> wrote:
> 
>    Hi,
> 
>    suppose I have the following theorem:
> 
>    th =
>    |- !x. P x = Q x
> 
>    How can I convert it into this one?
> 
>    |- !x. P x ==> Q x
> 
>    As the first step, I tried "ONCE_REWRITE_RULE [EQ_IMP_THM] th", and got 
> this:
> 
>    |- !x. (P x ==> Q x) /\ (Q x ==> P x)
> 
>    But then I don’t know how to benefit from AND1_THM (|- ∀t1 t2. t1 ∧ t2 ⇒ 
> t1), or there’s a better method to do the whole thing?
> 
>    Regards,
> 
>    Chun Tian
> 
> 
> 

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