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D.15.20.18 grsyz
Procedure from library gradedModules.lib (see gradedModules_lib).
- Usage:
- grsyz(M), graded object M
- Return:
- graded object
- Purpose:
- compute graded syzygy of M
Example:
| LIB "gradedModules.lib";
ring r=32003,(x,y,z),dp;
module A = grgroebner( grobj( module([x+y, x, 0, 3], [0, x+y, y, 2], [y, y, z, 1]), intvec(0,0,0,1) ) );
grview(A);
==> Graded homomorphism: r^3 + r(-1) <- r(-1)^3 + r(-2) + r(-3), given by a m\
atrix, with degrees:
==> ..1 ..2 ..3 ..4 ..5 ....
==> --- --- --- --- --- +...
==> 0 : 1 1 1 2 - |..1
==> 0 : 1 - 1 - - |..2
==> 0 : 1 1 1 2 3 |..3
==> 1 : 0 0 0 1 2 |..4
==> === === === === ===
==> 1 1 1 2 3
grview(grsyz(A));
==> Graded homomorphism: r(-1)^3 + r(-2) + r(-3) <- r(-2) + r(-3), given by a\
matrix, with degrees:
==> ..1 ..2 ....
==> --- --- +...
==> 1 : 1 - |..1
==> 1 : 1 2 |..2
==> 1 : 1 - |..3
==> 2 : 0 1 |..4
==> 3 : - 0 |..5
==> === ===
==> 2 3
module X = grgroebner( grobj( module([x]), intvec(2) ) );
grview(X);
==> Graded homomorphism: r(-2) <- r(-3), given by a diagonal matrix, with deg\
rees:
==> .1 ...
==> -- +..
==> 2 : 1 |.1
==> ==
==> 3
// syzygy module should be zero!
grview(grsyz(X));
==> Graded homomorphism: r(-3) <- 0, given by zero (1 x 0) matrix.
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