Fix PreImagesRepresentative for IsToPcGroupHomomorphismByImages
#5705
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Added a check whether the given element is in the image of the map. Now the method returns `fail` if not, as is specified in the documentation of `PreImagesRepresentative`. Note that `InversePcgs` is called (only) in the `PreImagesRepresentative` method for a group homomorphism in `IsToPcGroupHomomorphismByImages`. It sets the component `rangePcgs`; the value is a pcgs for the *image* of the homomorphism (in general *not* for the range).
ThomasBreuer
added
kind: bug
hulpke
reviewed
Apr 23, 2024
Yes, see #5073. |
hulpke
approved these changes
Apr 23, 2024
fingolfin
changed the title
PreImagesRepresentative for IsToPcGroupHomomorphismByImagesPreImagesRepresentative for IsToPcGroupHomomorphismByImages
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Added a check whether the given element is in the image of the map. Now the method returns
failif not, as is specified in the documentation ofPreImagesRepresentative.Note that
InversePcgsis called (only) in thePreImagesRepresentativemethod for a group homomorphism inIsToPcGroupHomomorphismByImages.It sets the component
rangePcgs; the value is a pcgs for the image of the homomorphism (in general not for the range).Resolves #5704, but there are likely other bugs of this kind.
I expect that #5073 or some follow-up of it will discuss the problem in the text for the release notes, thus there is no need to mention the current pull request in the release notes.