[Maxima-bugs] [maxima:bugs] #3688 declare symmetric changes indices in assignment

[Robert D. <rob...@us...>]

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** [bugs:#3688] declare symmetric changes indices in assignment**

**Status:** open
**Group:** None
**Labels:** declare symmetric array 
**Created:** Sun Dec 13, 2020 07:39 PM UTC by Robert Dodier
**Last Updated:** Sun Dec 13, 2020 07:39 PM UTC
**Owner:** nobody


Quoted from bug report #3664. Making a separate report here since this is a separate topic.

Dan Hayes writes:
~~~~
(n:3,kill(cm,m,mg), m[1]:ident(2),declare(mg,symmetric),mg:ident(3),for i thru 3 do cm[i]:zeromatrix(3,3),m[1][2,2]:-1,for i:2 thru 3 do
m[i]:zeromatrix(2,2),m[2][1,2]:1,m[3][2,1]:1,for i thru 3 do for j:i+1 thru 3 do( t:m[i].m[j]-m[j].m[i],disp([i,j,t])),cm[1][2,2]:2
,cm[2][1,2]:-2,cm[1][3,3]:-2,cm[3][1,3]:2,cm[2][3,1]:1,cm[3][2,1]:-1,for i thru 3 do(mg[i,i]:sum((cm[i].cm[i])[k,k],k,1,3),for j:i+1
thru 3 do(mg[i,j]:sum((cm[i].cm[j])[k,k],k,1,3),mg[j,i]:mg[i,j]) ),determinant(mg))
~~~~
the determinant(mg) should be -128 but i get 0 here because it gives mg[3,2] wrongly as 0 as if the command `mg[j,i]:mg[i,j]` was not there
which i should not have to put in anyway since i declared it symmetric but leaving it out did not work either
now when i take out the `declare(mg,symmetric)` then it does give the correct -128.



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