[EMAIL PROTECTED] writes:
> For symbolic computation can Axiom recognize that matrix multiplication in
> general does not commute, that is, for square matrices A and B, AB is not (in
> general) equal to BA?
Well, currently, there is no domain specially geared towards symbolic matrix
calculations, however:
* if you know the dimensions (and they are not too big), you do not have a
problem at all, just use generic matrices
* otherwise, you can use a noncommutative polynomial ring, for example XPOLY:
(1) -> p1:XPOLY INT := x+y
(1) x 1 + y 1
Type: XPolynomial Integer
(2) -> p2:XPOLY INT := x-y
(2) x 1 + y(- 1)
Type: XPolynomial Integer
(3) -> p1*p2
(3) x(x 1 + y(- 1)) + y(x 1 + y(- 1))
Type: XPolynomial Integer
(4) -> p2*p1
(4) x(x 1 + y 1) + y(x(- 1) + y(- 1))
Type: XPolynomial Integer
(5) -> p1*p2-p2*p1
(5) x y(- 2) + y x 2
Type: XPolynomial Integer
* if you need more general expressions in variables, you will probably have to
build your own domain, unfortunately.
Hope this helps,
Martin
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