Synopsis:
f_[i,j,k] -- extract some columns of blocks from a matrix f.
The source of f should be a direct sum, and the result is obtained by composition with the inclusion into the sum of the components numbered i, j, k. Free modules are regarded as direct sums.
i1 : f = map(ZZ^2 ++ ZZ^2, ZZ^2, {{1,2},{3,4},{5,6},{7,8}}) |
i2 : f^[0] |
i3 : f^[1] |
i4 : f^[1,0] |
See also:
Code:
-- ../../../Macaulay2-0.9.2/Macaulay2/m2/matrix1.m2:658 Matrix _ Array := Matrix => (f,v) -> f * (source f)_v