matrix construction.



mat_unblocker(matrix([0*A,A],[B,0*B]))

or

addrow(addcol(0*A,A),addcol(B,0*B))

or

mat_0ab0(A,B):=block([size:length(A)],  genmatrix( lambda([i,j],if i > size
and j <= size then A[i+size,j] elseif i<=size and j>=size then B[i,j+size]
else 0),size*2,size*2)

                 -s

On Thu, Aug 16, 2012 at 6:19 PM, John Lawvere <johnlawvere at yahoo.com> wrote:

> Hello:
>   Does anyone know an easy to do the following with maxima:
>    Given two n-by-n matrices: A and B, create a 2n-by-2n matrix, C, in
> which A is the upper right submatrix, B is the lower left submatrix, and
> the other 2 submatrices are all zero?
>
>   Sincerely,
>    John Lawvere
>
>
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>