Yes, this is a bug (can you open an issue for it?). It looks like the
expression is correct, but the printer isn't putting parentheses
around the (-B + A).

Aaron Meurer

On Fri, Nov 4, 2016 at 2:37 PM, Nathan Thern <[email protected]> wrote:
> Does this session illustrate a bug, or am I missing a concept here?
>
> Jupyter console 5.0.0
> Python 3.5.2 (v3.5.2:4def2a2901a5, Jun 25 2016, 22:01:18) [MSC v.1900 32 bit
> (Intel)]
> Type "copyright", "credits" or "license" for more information.
> IPython 5.1.0 -- An enhanced Interactive Python.
> ?         -> Introduction and overview of IPython's features.
> %quickref -> Quick reference.
> help      -> Python's own help system.
> object?   -> Details about 'object', use 'object??' for extra details.
>
> In [1]: import sympy
> In [2]: sympy.__version__
> Out[2]: '1.0'
> In [3]: from sympy import *
> In [4]: A=MatrixSymbol('A',1,3)
> In [5]: B=MatrixSymbol('B',1,3)
> In [6]: C=MatrixSymbol('C',1,3)
> In [7]: E=A-B
> In [8]: F=C[0,0]
> In [9]: F.subs(C,E)
> Out[9]: (-1)*B + A[0, 0]
> In [10]:
>
>
> I would think the output of the last command should be
> (-1)*B[0,0] + A[0, 0]
>
>
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