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D.15.6.1 grobj

Procedure from library gradedModules.lib (see gradedModules_lib).

Usage:
grobj(M, w[, d]), matrix/ideal/module M, intvec w, d

Return:
graded object with matrix presentation M, row weighting w [and total graded degrees d of columns]

Purpose:
create a valid graded object with a given matrix presentation, weighting [and total graded degrees (in case of zero columns)]

Example:
 
LIB "gradedModules.lib";
ring r=32003,(x,y,z),dp;
def A = grobj( module([x+y, x, 0, 0], [0, x+y, y, 0]), intvec(0,0,0,1) );
grview(A);
==> Graded homomorphism: r^3 + r(-1) <- r(-1)^2, given by a matrix, with degr\
   ees: 
==>      ..1 ..2 ....
==>      --- --- +...
==>   0 :  1   - |..1
==>   0 :  1   1 |..2
==>   0 :  -   1 |..3
==>   1 :  -   - |..4
==>      === ===     
==>        1   1     
def F = grobj( module([x,y,0]), intvec(1,1,5) );
grview(F);
==> Graded homomorphism: r(-1)^2 + r(-5) <- r(-2), given by a matrix, with de\
   grees: 
==>      ..1 ....
==>      --- +...
==>   1 :  1 |..1
==>   1 :  1 |..2
==>   5 :  - |..3
==>      ===     
==>        2     
int d = 666; // zero can have any degree...
def Z = grobj( module([x,0], [0,0,0], [0, y]), intvec(1,2,3), intvec(2, d, 3) );
grview(Z);
==> Graded homomorphism: r(-1) + r(-2) + r(-3) <- r(-2) + r(-666) + r(-3), gi\
   ven by a square matrix, with degrees: 
==>       ...1 ...2 ...3 .....
==>       ---- ---- ---- +....
==>    1 :   1    -    - |...1
==>    2 :   -    -    1 |...2
==>    3 :   -    -    - |...3
==>       ==== ==== ====      
==>          2  666    3      
print(Z);
==> x,0,0,
==> 0,0,y,
==> 0,0,0 
attrib(Z);
==> attr:degHomog, type intvec 
==> attr:isHomog, type intvec 
grrange(Z); // module weights
==> 1,2,3
attrib(Z, "degHomog"); // total degrees
==> 2,666,3
// Zero object:
matrix z[3][0];  grview( grobj( z, intvec(1,2,3) ) );
==> Graded homomorphism: r(-1) + r(-2) + r(-3) <- 0, given by zero (3 x 0) ma\
   trix.
grview( grobj( freemodule(0), intvec(1,2,3) ) );
==> Graded homomorphism: r(-1) + r(-2) + r(-3) <- 0, given by zero (3 x 0) ma\
   trix.
matrix z1[0][3]; grview( grobj( z1, 0:0, intvec(1,2,3) ) );
==> Graded homomorphism: 0 <- r(-1) + r(-2) + r(-3), given by zero (0 x 3) ma\
   trix.
grview( grobj( freemodule(0), 0:0, intvec(1,2,3) ) );
==> Graded homomorphism: 0 <- r(-1) + r(-2) + r(-3), given by zero (0 x 3) ma\
   trix.
matrix z0[0][0]; grview( grobj( z0, 0:0 ) );
==> Graded homomorphism: 0 <- 0, given by zero (0^2) matrix.
grview( grobj( freemodule(0), 0:0 ) );
==> Graded homomorphism: 0 <- 0, given by zero (0^2) matrix.


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