Goto Chapter: Top 1 2 Ind
 [Top of Book]  [Contents]   [Previous Chapter]   [Next Chapter] 

2 Examples and Tests
 2.1 Basic Commands

2 Examples and Tests

2.1 Basic Commands

gap> Q := HomalgFieldOfRationals();;
gap> a := VectorSpaceObject( 3, Q );
<A vector space object over Q of dimension 3>
gap> b := VectorSpaceObject( 4, Q );
<A vector space object over Q of dimension 4>
gap> homalg_matrix := HomalgMatrix( [ [ 1, 0, 0, 0 ],
>                                   [ 0, 1, 0, -1 ],
>                                   [ -1, 0, 2, 1 ] ], 3, 4, Q );
<A 3 x 4 matrix over an internal ring>
gap> alpha := VectorSpaceMorphism( a, homalg_matrix, b );
<A morphism in Category of matrices over Q>
gap> Display( alpha );
[ [   1,   0,   0,   0 ],
  [   0,   1,   0,  -1 ],
  [  -1,   0,   2,   1 ] ]

A morphism in Category of matrices over Q
gap> homalg_matrix := HomalgMatrix( [ [ 1, 1, 0, 0 ],
>                                   [ 0, 1, 0, -1 ],
>                                   [ -1, 0, 2, 1 ] ], 3, 4, Q );
<A 3 x 4 matrix over an internal ring>
gap> beta := VectorSpaceMorphism( a, homalg_matrix, b );
<A morphism in Category of matrices over Q>
gap> CokernelObject( alpha );
<A vector space object over Q of dimension 1>
gap> c := CokernelProjection( alpha );;
gap> Display( c );
[ [     0 ],
  [     1 ],
  [  -1/2 ],
  [     1 ] ]

A split epimorphism in Category of matrices over Q
gap> gamma := UniversalMorphismIntoDirectSum( [ c, c ] );;
gap> Display( gamma );
[ [     0,     0 ],
  [     1,     1 ],
  [  -1/2,  -1/2 ],
  [     1,     1 ] ]

A morphism in Category of matrices over Q
gap> colift := CokernelColift( alpha, gamma );;
gap> IsEqualForMorphisms( PreCompose( c, colift ), gamma );
true
gap> FiberProduct( alpha, beta );
<A vector space object over Q of dimension 2>
gap> F := FiberProduct( alpha, beta );
<A vector space object over Q of dimension 2>
gap> p1 := ProjectionInFactorOfFiberProduct( [ alpha, beta ], 1 );
<A morphism in Category of matrices over Q>
gap> Display( PreCompose( p1, alpha ) );
[ [   0,   1,   0,  -1 ],
  [  -1,   0,   2,   1 ] ]

A morphism in Category of matrices over Q
gap> Pushout( alpha, beta );
<A vector space object over Q of dimension 5>
gap> i1 := InjectionOfCofactorOfPushout( [ alpha, beta ], 1 );
<A morphism in Category of matrices over Q>
gap> i2 := InjectionOfCofactorOfPushout( [ alpha, beta ], 2 );
<A morphism in Category of matrices over Q>
gap> u := UniversalMorphismFromDirectSum( [ b, b ], [ i1, i2 ] );
<A morphism in Category of matrices over Q>
gap> Display( u );
[ [     0,     1,     1,     0,     0 ],
  [     1,     0,     1,     0,    -1 ],
  [  -1/2,     0,   1/2,     1,   1/2 ],
  [     1,     0,     0,     0,     0 ],
  [     0,     1,     0,     0,     0 ],
  [     0,     0,     1,     0,     0 ],
  [     0,     0,     0,     1,     0 ],
  [     0,     0,     0,     0,     1 ] ]

A morphism in Category of matrices over Q
gap> KernelObjectFunctorial( u, IdentityMorphism( Source( u ) ), u ) = IdentityMorphism( VectorSpaceObject( 3, Q ) );
true
gap> IsZero( CokernelObjectFunctorial( u, IdentityMorphism( Range( u ) ), u ) );
true
gap> DirectProductFunctorial( [ u, u ] ) = DirectSumFunctorial( [ u, u ] );
true
gap> CoproductFunctorial( [ u, u ] ) = DirectSumFunctorial( [ u, u ] );
true
gap> IsOne( FiberProductFunctorial( [ u, u ], [ IdentityMorphism( Source( u ) ), IdentityMorphism( Source( u ) ) ], [ u, u ] ) );
true
gap> IsOne( PushoutFunctorial( [ u, u ], [ IdentityMorphism( Range( u ) ), IdentityMorphism( Range( u ) ) ], [ u, u ] ) );
true
gap> IsCongruentForMorphisms( (1/2) * alpha, alpha * (1/2) );
true
gap> Dimension( HomomorphismStructureOnObjects( a, b ) ) = Dimension( a ) * Dimension( b );
true
gap> IsCongruentForMorphisms(
>     PreCompose( [ u, DualOnMorphisms( i1 ), DualOnMorphisms( alpha ) ] ),
>     InterpretMorphismFromDinstinguishedObjectToHomomorphismStructureAsMorphism( Source( u ), Source( alpha ),
>          PreCompose(
>              InterpretMorphismAsMorphismFromDinstinguishedObjectToHomomorphismStructure( DualOnMorphisms( i1 ) ),
>              HomomorphismStructureOnMorphisms( u, DualOnMorphisms( alpha ) )
>          )
>     )
> );
true
gap> vec := CapCategory( alpha );;
gap> t := TensorUnit( vec );;
gap> z := ZeroObject( vec );;
gap> IsCongruentForMorphisms(
>     ZeroObjectFunctorial( vec ),
>     InterpretMorphismFromDinstinguishedObjectToHomomorphismStructureAsMorphism( z, z, ZeroMorphism( t, z ) )
> );
true
gap> IsCongruentForMorphisms(
>     ZeroObjectFunctorial( vec ),
>     InterpretMorphismFromDinstinguishedObjectToHomomorphismStructureAsMorphism(
>         z, z,
>         InterpretMorphismAsMorphismFromDinstinguishedObjectToHomomorphismStructure( ZeroObjectFunctorial( vec ) )
>     )
> );
true
gap> right_side := PreCompose( [ i1, DualOnMorphisms( u ), u ] );;
gap> x := SolveLinearSystemInAbCategory( [ [ i1 ] ], [ [ u ] ], [ right_side ] )[1];;
gap> IsCongruentForMorphisms( PreCompose( [ i1, x, u ] ), right_side );
true
 [Top of Book]  [Contents]   [Previous Chapter]   [Next Chapter] 
Goto Chapter: Top 1 2 Ind

generated by GAPDoc2HTML