5.1.2 attrib

Syntax:

attrib ( name )

Type:

none

Purpose:

displays the attribute list of the object called name.

Example:

ring r=0,(x,y,z),dp; ideal I=std(maxideal(2)); attrib(I); ==> attr:isSB, type int

Syntax:

attrib ( name , string_expression )

Type:

any

Purpose:

returns the value of the attribute string_expression of the variable name. If the attribute is not defined for this variable, attrib returns the empty string.

Example:

ring r=0,(x,y,z),dp; ideal I=std(maxideal(2)); attrib(I,"isSB"); ==> 1 // maxideal(2) is a standard basis, // SINGULAR does know it for maxideal: attrib(maxideal(2), "isSB"); ==> 1

Syntax:

attrib ( name, string_expression, expression )

Type:

none

Purpose:

sets the attribute string_expression of the variable name to the value expression.

Example:

ring r=0,(x,y,z),dp; ideal I=maxideal(2); // the attribute "isSB" is not set vdim(I); ==> 4 attrib(I,"isSB",0); // the standard basis attribute is reset here vdim(I); ==> // ** I is no standard basis ==> 4

Remark:

An attribute may be described by any string_expression. Some of these are used by the kernel of SINGULAR and referred to as reserved attributes. Non-reserved attributes may be used, however, in procedures and can considerably speed up computations.

Reserved attributes:

(cf_class, global, isSB, isHomog, rank, ring_cf, rowShift are used by the kernel, the other are used by libraries)

cf_class (for ring)

the internal type of the coefficients (see n_coeffType)

global (for ring)

1, if the ordering is global

isSB (for ideal, module)

the standard basis property is set by all commands computing a standard basis like groebner, std, stdhilb etc.; used by lift, dim, degree, mult, hilb, vdim, kbase

isHomog (for ideal, module)

the weight vector of module generators for homogeneous or quasihomogeneous ideals/modules,
used by betti, degree, highcorner, hilbert, homog, prune, prune_map, sba, slimgb, std, syz, kbase, modulo, mres, mres_map, nres, stdhilb.

isCI

complete intersection property

isCM

Cohen-Macaulay property

maxExp (for ring/list from ringlist)

limit for each exponent (32767 by default)

rank (for module)

set/get the rank of a module (see nrows)

ring_cf (for ring)

the coefficients of the polynomial ring are considered to be a ring

withSB

value of type ideal, resp. module, is std

withHilb

value of type intvec is hilb(_,1) (see hilb)

withRes

value of type list is a free resolution

withDim

value of type int is the dimension (see dim)

withMult

value of type int is the multiplicity (see mult)