86.5 DirectSumMat

DirectSumMat( mat1, ... , matn )

returns the block diagonal direct sum of the matrices mat1, ldots, matn.

    gap> C1 := [ [   2,  -1,   0,   0 ],
    >            [  -1,   2,  -1,   0 ],
    >            [   0,  -1,   2,  -1 ],
    >            [   0,   0,  -1,   2 ] ];;
    gap> C2 := [ [   2,   0,  -1,   0 ],
    >            [   0,   2,  -1,   0 ],
    >            [  -1,  -1,   2,  -1 ],
    >            [   0,   0,  -1,   2 ] ];;
    gap> d := DirectSumMat( C1, C2 );;
    gap> PrintArray( d );
    [ [   2,  -1,   0,   0,   0,   0,   0,   0 ],
      [  -1,   2,  -1,   0,   0,   0,   0,   0 ],
      [   0,  -1,   2,  -1,   0,   0,   0,   0 ],
      [   0,   0,  -1,   2,   0,   0,   0,   0 ],
      [   0,   0,   0,   0,   2,   0,  -1,   0 ],
      [   0,   0,   0,   0,   0,   2,  -1,   0 ],
      [   0,   0,   0,   0,  -1,  -1,   2,  -1 ],
      [   0,   0,   0,   0,   0,   0,  -1,   2 ] ] 

One can also use a computed list of matrices as an argument; the function call then reads ApplyFunc(DirectSumMat, [mat1, ... , matn] ). Previous Up Top Next
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