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MathGroup Archive 1998

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Please help: How to assert that an object is a matrix ???




Hi, everyone!

I'm trying to analyse the block structure of a matrix in Mathematica to
figure out the best way to solve a system with this matrix. 

For example I write 

	A := {{GL,0,0,0,IL[1]},
		{GT,0,0,0,0},
		{0,GL,0,0, IL[2]},
		{0,GT,0,0,0},
		{0,0,GL,0,IL[3]},
		{0,0, GT,0,0},
		{0,0,0,GL,IL[4]},
		{0,0,0,GT,0}}
	X := {XP1,XP2,XP3,XP4,XL}
	B := {0,PT[1],0,PT[2],0,PT[3],0,PT[4]}

where GL, GT, IL, etc., are not elements but (sub-)matrices themself. I
want to perform algebraic transformations on A, but I want element
multiplication to be non-commutative and inversion to use Inverse
rather than 1/element.

Can I somehow trick Mathematica to assume that elements are matrices? 

Any help is appreciated!

Paul

-- 
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