25.83 SumAgGroup

SumAgGroup( V, W )

Let V and W be ag groups with a common parent group, such that <W> leq N (<V>). Then <V> * <W> is a subgroup and SumAgGroup returns <V> * <W>.

The function uses the Zassenhaus sum-intersection algorithm (see GS90).

Note that this functions returns an incorrect result if <W> not leq N(<V>).

    gap> d8_1 := Subgroup( s4, [ a, c, d ] );
    Subgroup( s4, [ a, c, d ] )
    gap> d8_2 := Subgroup( s4, [ a*b, c, d ] );
    Subgroup( s4, [ a*b, c, d ] )
    gap> SumAgGroup( d8_1, d8_2 );
    Group( a*b, b^2, c, d ) 

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