There are only 19 theorems, as a few of them have multiple hypotheses and
are being double counted.

But to me, this is not the relevant metric when it comes to analyzing the
impact of such a change. What matters is, of the 70 deduction theorems that
*don't* use a hypothesis in substitutions, how many uses do they
(collectively) have, and what percentage of those uses would get simpler
with the deduction? Consider that there is a theorem oveq1: |- ( A = B -> (
A + C ) = ( B + C ) ), but no theorem |- ( ( ph /\ A = B ) -> ( A + C ) = (
B + C ) ), so a proof that uses this would get one step longer (to either
use oveq1d + simpr or adantl + oveq1). I would guess that most uses fall
into this category, with only a small fraction going into the category that
is doing substitution and substantive steps separately rather than
simultaneously (at the cost of 5 or 6 steps).

On Mon, Nov 4, 2019 at 1:00 AM 'Alexander van der Vekens' via Metamath <
[email protected]> wrote:

> Hi Thierry,
> yes, you are right - the second list contains also theorems of the
> mathboxes. Here is the list containing only the 23 theorems of the main
> part.
>
> On Sunday, November 3, 2019 at 11:44:23 PM UTC+1, Thierry Arnoux wrote:
>>
>> Hi Alexander,
>>
>> For the second list, did you also restrict yourself to the main part of
>> set.mm ?
>> BR,
>> _
>> Thierry
>>
>> Le 3 nov. 2019 à 23:38, 'Alexander van der Vekens' via Metamath <
>> [email protected]> a écrit :
>>
>> 
>>
>> On Thursday, October 31, 2019 at 1:55:27 PM UTC+1, Norman Megill wrote:
>>
>>>
>>> We could add ph to every such hypothesis to make it more
>>> general-purpose, but 99% of the time it wouldn't be needed and would make
>>> all other proofs using it (as well as the theorem itself) slightly longer.
>>> Not to mention that it would be a huge retrofit to do this throughout
>>> set.mm.  I will concede there may be a few cases where it would be
>>> advantageous to do things other than prove a simple substitution with the
>>> hypothesis, but overall I believe it is rare and does not justify adding ph
>>> everywhere.
>>>
>>> I tried to identify all the theorems in set.mm (excluding the
>> mathboxes) which would be concerned - I found about 70 of them (see
>> attachment deduct_th_eq_hyp.txt). On the other hand, there are about 50
>> theorema in deduction form having the form $e |- ( ( ph /\ x = ... ) -> ...
>> ) $. (see attachment deduct_th_ph_eq_hyp.txt). So there is no big
>> difference. Therefore, I still would propose to recommend to use the form
>> $e |- ( ( ph /\ x = ... ) -> ... ) $. in deduction style. Already existing
>> theorems need not to be rewritten (by the way, many of them have no "d" at
>> the end..).
>>
>>>
>>>
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>> <deduct_th_ph_eq_hyp.txt>
>> <deduct_th_eq_hyp.txt>
>>
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