Thanks everyone!

Glauco, if you are interested, I was able to shorten 3 other proofs in your 
mathbox, they are: n0p (339 to 330 bytes), unima (412 to 79 bytes), and 
nelrnresa (87 to 58 bytes), all of them rely on the same, or a subset of 
the axioms originally used.  Let me know if you want to see them and I will 
post them here!

On Thursday, April 22, 2021 at 1:43:51 PM UTC-4 Glauco wrote:

> Did I really write it? :-)
>
> It looks like I wrote it when I was proving the Stone Weierstrass theorem, 
> and that's been my first theorem in mm.
>
> Back then, the whole framework was new to me, and I guess that the (sad) 
> simple explanation is that I didn't know I was just one a1i away from ovex.
>
> Thanks for the post, added to the refactor/cleanup mathbox to-do list.
>
>
> Glauco
>
> Il giorno giovedì 22 aprile 2021 alle 04:15:04 UTC+2 [email protected] ha 
> scritto:
>
>> It is a bit of a strange theorem. I see that it is in Glauco's mathbox 
>> (and referenced a few times), and both the proof and the uses can be 
>> simplified using ovex, but perhaps there is something that they were trying 
>> to avoid (not axioms, the axiom list is a strict subset with the new 
>> proof). Perhaps they can chime in here.
>>
>> On Wed, Apr 21, 2021 at 9:48 PM Jim Kingdon <[email protected]> wrote:
>>
>>> On 4/21/21 5:37 PM, Kyle Wyonch wrote:
>>>
>>> > I was wondering if this shortening [of cnfex] was valid
>>>
>>> Short answer is, yes it is valid.
>>>
>>> The longer answer is that set.mm defines a function evaluated outside 
>>> its domain to be the empty set which is why 
>>> http://us.metamath.org/mpeuni/fvex.html does not have any conditions.
>>>
>>> By contrast, iset.mm does not have the ability to do quite this, so 
>>> instead cnfex would need to use 
>>> http://us.metamath.org/ileuni/funfvex.html or one of the other 
>>> alternatives under fvex at http://us.metamath.org/ileuni/mmil.html#setmm
>>>
>>> There is some discussion of this in the "undefined results" section of 
>>> http://us.metamath.org/mpeuni/conventions.html and 
>>> http://us.metamath.org/ileuni/conventions.html
>>>
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>>> .
>>>
>>

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