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11 Free distributive completion of a finitely presented category
 11.1 Constructors
 11.2 Attributes
 11.3 GAP Categories
 11.4 Examples

11 Free distributive completion of a finitely presented category

11.1 Constructors

11.1-1 FreeDistributiveCompletion
‣ FreeDistributiveCompletion( B )( operation )
‣ FreeDistributiveCompletion( B, H )( operation )

Returns: a CAP category

Construct a free distributive completion category.

11.2 Attributes

11.2-1 UnderlyingCategory
‣ UnderlyingCategory( finite_completion )( attribute )

11.2-2 EmbeddingOfUnderlyingCategory
‣ EmbeddingOfUnderlyingCategory( finite_completion )( attribute )

Returns: a CAP functor

11.3 GAP Categories

11.3-1 IsFreeDistributiveCompletion
‣ IsFreeDistributiveCompletion( category )( category )

Returns: true or false

The GAP category of a free distributive completion category.

11.3-2 IsCellInFreeDistributiveCompletion
‣ IsCellInFreeDistributiveCompletion( cell )( category )

Returns: true or false

The GAP category of cells in a free distributive completion category.

11.3-3 IsObjectInFreeDistributiveCompletion
‣ IsObjectInFreeDistributiveCompletion( obj )( category )

Returns: true or false

The GAP category of objects in a free distributive completion category.

11.3-4 IsMorphismInFreeDistributiveCompletion
‣ IsMorphismInFreeDistributiveCompletion( mor )( category )

Returns: true or false

The GAP category of morphisms in a free distributive completion category.

11.4 Examples

11.4-1 Second Dedekind number

The category of presheaves with values in the interval category of the boolean algebra 2^2 has 6 distinct objects. This is the free distributive lattice generated by a discrete category with two objects.

gap> LoadPackage( "FunctorCategories", false );
true
gap> pq := FinQuiver( "quiver(p,q)" );
FinQuiver( "quiver(p,q)[]" )
gap> F := PathCategory( pq );
PathCategory( FinQuiver( "quiver(p,q)[]" ) )
gap> P := PosetOfCategory( F );
PosetOfCategory( PathCategory( FinQuiver( "quiver(p,q)[]" ) ) )
gap> Dist := FreeDistributiveCompletion( P );
FreeDistributiveCompletion(
PosetOfCategory( PathCategory( FinQuiver( "quiver(p,q)[]" ) ) ) )
gap> Display( Dist );
A CAP category with name FreeDistributiveCompletion(
PosetOfCategory( PathCategory( FinQuiver( "quiver(p,q)[]" ) ) ) ):

25 primitive operations were used to derive 293 operations for this category
which algorithmically
* IsCategoryWithDecidableColifts
* IsCategoryWithDecidableLifts
* IsFiniteCategory
* IsEquippedWithHomomorphismStructure
* IsHeytingAlgebra
and not yet algorithmically
* IsBiHeytingAlgebra
gap> Length( SetOfObjects( Dist ) );
6
gap> Print( DotVertexLabelledDigraph( DigraphOfPoset( Dist : offset := 0 ) ) );
//dot
digraph subobject_lattice{
rankdir="BT"
minlen=0
node [shape=circle width=0 height=0 fontsize=12 margin=0.01 fontname="DejaVu Serif,serif"]
edge [arrowsize=0.5]
1 [label="0"]
2 [label="1"]
3 [label="2"]
4 [label="3"]
5 [label="4"]
6 [label="5"]
1 -> 5
3 -> 6
4 -> 6
5 -> 3
5 -> 4
6 -> 2
}
gap> DiffbCSL := MeetSemilatticeOfSingleDifferences( Dist );
MeetSemilatticeOfSingleDifferences( FreeDistributiveCompletion(
PosetOfCategory( PathCategory( FinQuiver( "quiver(p,q)[]" ) ) ) ) )
gap> Length( SetOfObjects( DiffbCSL ) );
13
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