Re: [Metamath] Question on definition of magma

2023-10-11 Thread Mario Carneiro
On Thu, Oct 12, 2023 at 1:46 AM bil...@gmail.com wrote: > I am at a more basic level than what you are trying to address. My goal is > to learn how to prove theorems in metamath. > > My current task is to do the follow: given B = { x | ph }, how would I > prove that A e. B. This is beginning

Re: [Metamath] Question on definition of magma

2023-10-11 Thread bil...@gmail.com
I am at a more basic level than what you are trying to address. My goal is to learn how to prove theorems in metamath. My current task is to do the follow: given B = { x | ph }, how would I prove that A e. B. This is beginning level stuff. I see that there is theorem elab2g that would be

Re: [Metamath] Question on definition of magma

2023-10-11 Thread Mario Carneiro
Usually we prioritize minimizing the length of the definition (number of symbols) over the length of the extraction theorem, because the former is an axiom and the latter is not. On Thu, Oct 12, 2023 at 12:46 AM bil...@gmail.com wrote: > You say that the definitions are the same, but to me

Re: [Metamath] Question on definition of magma

2023-10-11 Thread bil...@gmail.com
You say that the definitions are the same, but to me "substitution" needs to be proved in a roundabout way: that is, it is not just substituting "( Base ` g )" for "b". The theorem ismgm that immediately follows the definition for Mgm requires 19 steps, whereas only 8 steps are needed for the

Re: [Metamath] Question on definition of magma

2023-10-11 Thread Mario Carneiro
Those two definitions are the same except you have removed the substitutions b := ( Base ` g ) and o := ( +g ` g ) . The substitutions are there to make the definition more readable (and usually shorter, although it might be a wash in a short definition like this one). For a more elaborate example

[Metamath] Question on definition of magma

2023-10-11 Thread bil...@gmail.com
The given definition of magma is: df-mgm |- Mgm = { g | [. ( Base ` g ) / b ]. [. ( +g ` g ) / o ]. A. x e. b A. y e. b ( x o y ) e. b } Would it be ok to define magma as follows: df-mgm |- Mgm = { g | A. x e. ( Base ` g ) A. y e. ( Base ` g ) ( x ( +g ` g ) y ) e. ( Base ` g ) } If so,