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Module ++ Module -- direct sum of modules

Synopsis

Operator: ++

Description

M++N -- computes the direct sum of two modules (or coherent sheaves).

i1 : R = ZZ/101[a..c];

i2 : image vars R ++ kernel vars R

o2 = image {0} | a b c 0  0  0  |
           {1} | 0 0 0 0  -b -c |
           {1} | 0 0 0 -c a  0  |
           {1} | 0 0 0 b  0  a  |

                             4
o2 : R-module, submodule of R

Projection and inclusion maps for direct sums:

Module ^ Array -- projection onto summand
Module _ Array -- get inclusion map into direct sum

See also

directSum -- direct sum of modules or maps