Problems when multiplying a matrix object with a matrix#6240
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ThomasBreuer wants to merge 5 commits intogap-system:masterfrom
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Problems when multiplying a matrix object with a matrix#6240ThomasBreuer wants to merge 5 commits intogap-system:masterfrom
ThomasBreuer wants to merge 5 commits intogap-system:masterfrom
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`IsGF2MatrixRep` and `Is8BitMatrixRep` describe matrices that are in `IsMatrix and IsMatrixObj`. Thus these matrices must obey the rules of list arithmetics, in particular the multiplication of these matrices with other matrices in `IsMatrix` is defined. Up to now, the methods that are chosen for such matrix multiplications are the generic methods. Now we install `PROD_LIST_SCL_DEFAULT` explicitly as a method. First of all, this removes some overhead. (Note that such multiplications really occur in practice, as one can see in the testfiles: For example, construct a matrix group with `CyclicGroup` or `GL`; the generators are in `IsGF2MatrixRep` or `Is8BitMatrixRep` if possible, due to `ImmutableMatrix`. Then construct a right coset of this group by prescribing a representative that is in `IsPlistRep`, and do some computations with it; multiplications "of mixed type" will happen.) Second, this yields high ranked methods such that it will be possible to install `\*` methods of lower rank that signal an error if one tries to multiply a *non-list* `IsMatrixObj` with an `IsMatrix`.
The multiplication of an `IsMatrixObj` that is *not* in `IsMatrix` with an `IsMatrix` shall not be allowed, the result is not defined (and the results without the new methods can be surprising).
Up to now, `ViewString` and `DisplayString` returned something that makes sense only for objects in `MatrixObj`, not for `IsMatrix`. (I had introduced this bug in 2021, apparently the two functions are not used, otherwise the problem would have been observed earlier.)
ThomasBreuer
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addresses #6221
The idea is to catch the multiplication of a non-list
IsMatrixObjwith anIsMatrixby dedicated methods for\*.For that, new
\*methods for the multiplication ofIsGF2MatrixRepwith anIsMatrixand ofIs8BitMatrixRepwithIsMatrixget installed; this is anyhow a good idea because these multiplications were up to now executed by the default list arithmetic.Besides that, the
DisplayStringandViewStringmethods forIsMatrixObjwere fixed; up to now, they were applicable also forIsMatrix.