Hi all,

I stumbled upon the discussion on matrix assumptions and the bit of history 
behind this sympy module:
http://scicomp.stackexchange.com/questions/74/symbolic-software-packages-for-matrix-expressions

First off all, thank you Matt, this is incredibly cool stuff!

Now, I'm trying to do some matrix algebra while encoding knowledge about 
the matrices involved. For instance, say my matrix U is unitary, i.e. U * 
U.T = I. I've looked around in the documentation and source code, but 
couldn't figure out, if the new assumption system can be used to simplify 
matrix expressions.

I was trying to exploit this using sympy as follows:

    from sympy import Q, symbols, MatrixSymbol, ask, simplify
    from sympy.assumptions.assume import global_assumptions

    n = symbols('n', integer=True)
    U = MatrixSymbol('U', n, n)

    global_assumptions.add(Q.unitary(U))

    UU = U * U.T
    
    print UU

    simpleUU = simplify(UU)
    print simpleUU
    

I was hoping that the second print would output the Identity, but somehow 
this didn't work. Any suggestions, pointers, hints?


Cheers,
Chris

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