next | previous | forward | backward | up | top | index | toc | Macaulay2 website
Polyhedra :: isComplete

isComplete -- checks completeness of a Fan or PolyhedralComplex



isComplete just calls an entry in the hash table of the Fan. The check for completeness is done while generating the fan. Whenever a full dimensional Cone is added (see fan or addCone) the set of faces of codimension 1 that appear only in one full dimensional Cone is updated. The Fan is then complete if and only if this set is empty and there is at least one full dimensional Cone.

For a PolyhedralComplex the function does the same. Just note, that a complete polyhedral complex must contain non-compact polyhedra.

i1 : C1 = coneFromVData matrix {{1,0},{0,1}};
i2 : C2 = coneFromVData matrix {{1,-1},{0,-2}};
i3 : C3 = coneFromVData matrix {{0,-2},{1,-1}};
i4 : F = fan {C1,C2,C3}

o4 = F

o4 : Fan
i5 : isComplete F

o5 = false

Hence the fan above is not complete, but we can add the missing cone:

i6 : C4 = coneFromVData matrix {{-1,-2},{-2,-1}};
i7 : F = addCone(C4,F)

o7 = F

o7 : Fan
i8 : isComplete F

o8 = true

Ways to use isComplete :

For the programmer

The object isComplete is a method function.