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Module _ Array -- get inclusion map into direct sum

Synopsis

Description

M_[i,j,k] -- get inclusion map of blocks from a module M.

The module M should be a direct sum, and the result is the matrix obtained by inclusion from the sum of the components numbered i, j, k. Free modules are regarded as direct sums.

This method works also for chain complexes.

i1 : M = ZZ^2 ++ ZZ^3

       5
o1 = ZZ

o1 : ZZ-module, free
i2 : M_[0]

o2 = | 1 0 |
     | 0 1 |
     | 0 0 |
     | 0 0 |
     | 0 0 |

              5        2
o2 : Matrix ZZ  <--- ZZ
i3 : M_[1]

o3 = | 0 0 0 |
     | 0 0 0 |
     | 1 0 0 |
     | 0 1 0 |
     | 0 0 1 |

              5        3
o3 : Matrix ZZ  <--- ZZ
i4 : M_[1,0]

o4 = | 0 0 0 1 0 |
     | 0 0 0 0 1 |
     | 1 0 0 0 0 |
     | 0 1 0 0 0 |
     | 0 0 1 0 0 |

              5        5
o4 : Matrix ZZ  <--- ZZ

See also