|
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 , sba , slimgb , std , syz ,
kbase , modulo , mres , 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)
See
killattrib.
|