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:

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

isSB

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

the weight vector for homogeneous or quasihomogeneous ideals/modules

isCI

complete intersection property

isCM

Cohen-Macaulay property

rank

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

ring_cf

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)