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5.1.1 attrib
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Syntax:
attrib ( name )
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Type:
none
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Purpose:
displays the attribute list of the object called name.
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Example:
| ring r=0,(x,y,z),dp;
ideal I=std(maxideal(2));
attrib(I);
→ attr:isSB, type int
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Syntax:
attrib ( name , string_expression )
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Type:
any
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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.
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Example:
| ring r=0,(x,y,z),dp;
ideal I=std(maxideal(2));
attrib(I,"isSB");
→ 1
// although maxideal(2) is a standard basis,
// SINGULAR does not know it:
attrib(maxideal(2), "isSB");
→ 0
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Syntax:
attrib ( name, string_expression, expression )
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Type:
none
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Purpose:
sets the attribute string_expression of the variable name
to the value expression.
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Example:
| ring r=0,(x,y,z),dp;
ideal I=maxideal(2); // the attribute "isSB" is not set
vdim(I);
→ // ** I is no standardbasis
→ 4
attrib(I,"isSB",1); // the standard basis attribute is set here
vdim(I);
→ 4
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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.
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Reserved attributes:
(not all are in use at the moment)
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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
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isHomog
the weight vector for homogeneous or quasihomogeneous ideals/modules
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isCI
complete intersection property
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isCM
Cohen-Macaulay property
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rank
set the rank of a module (see nrows)
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withSB
value of type ideal, resp. module, is std
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withHilb
value of type intvec is hilb(_,1) (see hilb)
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withRes
value of type list is a free resolution
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withDim
value of type int is the dimension (see dim)
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withMult
value of type int is the multiplicity (see mult)
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