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Dear GAP - Forum,

I think there is a bug in ResidueClassOps.Intersection in GAP 3.4.4 :

The two arguments in the call of ChineseRem are in wrong order :

the first argument has to be the moduli and the second one the residues.

This bug certainly leads to wrong results, for example :

gap> x := ResidueClass(2,7); ResidueClass( 2, 7 ) gap> y := ResidueClass(3,11); ResidueClass( 3, 11 ); gap> z := Intersection(x,y); ResidueClass( 5, 77 ) # The right answer would be 'ResidueClass ( 58, 77 )'

This bug also appears in the manual on page 198.

Another question :

Why is GAP not able to compute associates in the ring of Gaussian

Integers ? :

gap> Associates(Integers,2);

[ -2, 2 ] # Correct

gap> Associates(GaussianIntegers,2);

Error, <D> must be a domain or a set in

Elements( Units( R ) ) called from

R.operations.Associates( R, r ) called from

Associates( GaussianIntegers, 2 ) called from

main loop

Stefan Kohl

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