Equivalence of expressions up to permutation of variables



In logic and theorem proving this is called "unification".  There is a huge
literature in it. Some restricted versions are fast, but mostly it is not.
RJF


> -----Original Message-----
> From: maxima-bounces at math.utexas.edu 
> [mailto:maxima-bounces at math.utexas.edu] On Behalf Of Chris Sangwin
> Sent: Wednesday, June 27, 2007 4:40 AM
> To: Maxima at math.utexas.edu
> Subject: Equivalence of expressions up to 
> permutation of variables
> 
> 
> Is there an existing Maxima function which will establish a possible 
> substitution of variables [v_i=u_i,... with the property that
> 
> subst(v_i=u_i,...,ex_1)=ex_2
> 
> The function should return the permutaion as a list of equations, or 
> false.
> 
> There are different notions of "equality" here including
>   (1) that above, based on Maxima's data structure and
>   (2) ratsimp(subst(v_i=u_i,...,ex_1)-ex_2)=0.
> 
> Any suggestions welcome, particularly any which do not rely on an 
> exhaustive search of the permutations of "n" variables!
> 
> Thanks
> Chris
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