| #### D.15.8.2 grtest Procedure from library `gradedModules.lib` (see gradedModules_lib). Usage: grtest(M[,b]), anything M, optionally int b Return: 1 if M is a valid graded object, 0 otherwise Purpose: validate a graded object. Print an invalid object message if b is not given Note: M should be an ideal or module or matrix, with weighting attribute 'isHomog' and optionally total graded degrees attribute 'degHomog'. Attributes should be compatible with the presentation matrix. Example:
    LIB "gradedModules.lib";
    ring r=32003,(x,y,z),dp;
    // the following calls will fail due to tests in grtest:
    grobj( module([x+y, x, 0, 0], [0, x+y, y, 0]), intvec(0,0,0,0) ); // enough row weights
    ==> _[1]=x*gen(2)+x*gen(1)+y*gen(1)
    ==> _[2]=x*gen(2)+y*gen(3)+y*gen(2)
    // grobj( module([x+y, x, 0, 0], [0, x+y, y, 0]), intvec(0,0) ); // not enough row weights
    // grobj( module([x,0], [0,0,0], [0, y]), intvec(1,2,3) ); // zero column needs (otherwise optional) total degrees
    grobj( module([x,0], [0,0,0], [0, y]), intvec(1,2,3), intvec(2, 10, 3) ); // compatible total degrees (on non-zero columns)
    ==> _[1]=x*gen(1)
    ==> _[2]=0
    ==> _[3]=y*gen(2)
    // grobj( module([x,0], [0,0,0], [0, y]), intvec(1,2,3), intvec(2-1, 10, 3+1) ); // incompatible total degrees (on both non-zero columns)

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