I guess you could reopen 2022. I would mark it blocked on 2026 if you think
that issue will solve [7] and [8].
Aaron Meurer
On Feb 14, 2011, at 2:06 PM, Julien Rioux wrote:
> Dear list,
>
> I found some more problems when using non-commutative symbols and subs
> and I wonder if I should reopen issue 2022 or open a new issue?
>
> In [1]: import sympy
>
> In [2]: print sympy.__version__
> 0.6.7-git
>
> In [3]: sympy.var('a b c')
> Out[3]: (a, b, c)
>
> In [4]: A=sympy.Symbol('A', commutative=False)
>
> In [5]: B=sympy.Symbol('B', commutative=False)
>
> In [6]: (a*A).subs(a*a*A,B)
> Out[6]: a*B
>
> In [7]: (A*A).subs(A*A*A,c)
> Out[7]: c**(2/3)
>
> In [8]: (A*A*A).subs(A*A,c)
> Out[8]: c**(3/2)
>
> In [6] and [7] no substitution should occur, in [8] c*A should be the result.
>
> [7] and [8] are related to issue 2026, but it's different in that with
> non-commutative symbols, it is simply wrong to do algebraic
> substitution.
>
> --
> Julien
>
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