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Properties of Incidence Structures and Designs
Properties of Incidence Structures and Designs
IsSimple(D) : Inc -> BoolElt
True iff the incidence structure D has no repeated blocks.
IsTrivial(D) : Inc -> BoolElt
True iff the incidence structure D is a trivial incidence structure.
IsSelfDual(D) : Inc -> BoolElt
True iff the incidence structure D is self-dual; i.e. if D is
isomorphic to its dual.
IsUniform(D) : Inc -> BoolElt, RngIntElt
True iff the incidence structure D is uniform; that is, each
block contains the same number of points. If true, also returns
the blocksize.
IsNearLinearSpace(D) : Inc -> BoolElt
True iff the incidence structure D is a near-linear space.
IsLinearSpace(D) : Inc -> BoolElt
True iff the incidence structure D is a linear space.
IsDesign(D, t: parameters) : Inc, RngIntElt -> BoolElt, RngIntElt
Al: MonStgElt Default: "NoOrbits"
True iff the incidence structure D is a t-design.
If true, then the number of blocks of D containing a general t-set is
also returned.
The optional parameter Al can be used to specify the algorithm
used for balance testing. The default value is "NoOrbits", which
applies a "brute force" test. The alternative is "Orbits", which
uses the orbits of t-sets under the automorphism group of D.
This is much faster for some cases, but slower for others.
IsBalanced(D, t: parameters) : Inc, RngIntElt -> BoolElt, RngIntElt
Al: MonStgElt Default: "NoOrbits"
True iff the incidence structure D is balanced (with respect to t).
If true, then the number of blocks of D containing a general t-set is
also returned.
The optional parameter Al can be used to specify the algorithm
used. The default value is "NoOrbits", which
applies a "brute force" test. The alternative is "Orbits", which
uses the orbits of t-sets under the automorphism group of D.
This is much faster for some cases, but slower for others.
IsResolvable(D) : Inc -> BoolElt, { SetEnum }
True iff there exists a resolution of the incidence structure D;
i.e. a partition of the blocks of D into parallel classes.
If true, also returns a resolution.
IsComplete(D) : Inc -> BoolElt
True iff D is the complete design.
IsSymmetric(D) : Dsgn -> BoolElt
True iff the design D is symmetric.
IsSteiner(D, t) : Dsgn -> BoolElt
True iff the design D is a Steiner t-design.
IsPointRegular(D) : IncNsp -> BoolElt, RngIntElt
True iff the (near-)linear space D is point regular.
If true, the point regularity is also returned.
IsLineRegular(D) : IncNsp -> BoolElt, RngIntElt
True iff the (near-)linear space D is line regular.
If true, the line regularity is also returned.
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