Make equality of factorizations give error (instead of false)

[JohnAAbbott]

Response to issue https://github.com/oscar-system/Oscar.jl/issues/5319#issuecomment-3405528665

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 87.95%. Comparing base (2980528) to head (7f40048).

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #2188   +/-   ##
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  Coverage   87.95%   87.95%           
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  Files         127      127           
  Lines       31791    31793    +2     
=======================================
+ Hits        27961    27963    +2     
  Misses       3830     3830           

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[simonbrandhorst]

Thanks a lot. Looks good to me. Can we merge?

[JohnAAbbott]

Quick question: the proposed implementation always gives an error except if a factorization is tested for equality against itself (in which case it returns true). Is this the behaviour that we want?

[thofma]

I would just make it error in all cases with the same error message.

[simonbrandhorst]

It is certainly an improvement over the existing state of things.
I can also live with always returning an error (no exception) ... but I don't think it matters. So let us get over with this.

[JohnAAbbott]

I hope to push some tests very soon....

[JohnAAbbott]

I would just make error in all cases with the same error message.

This is probably simplest until we find a better idea inspired by a genuine use-case. It does still "feel strange" that comparing a factorization with itself triggers an error (rather than returning true), but triggering an error even in this case does emphasize that factorizations cannot be equality-tested.

I suppose I had better just delete the more involved code I first pushed -- extra complexity for no purpose?

[thofma]

This is probably simplest until we find a better idea inspired by a genuine use-case. It does still "feel strange" that comparing a factorization with itself triggers an error (rather than returning true), but triggering an error even in this case does emphasize that factorizations cannot be equality-tested.

The problem with just testing F1 === F2 is that for F = factor(5) one has F == F evaluate to true but factor(5) == factor(5) evaluates to false. I would not consider this an advantage over just always throwing an error.

I suppose I had better just delete the more involved code I first pushed -- extra complexity for no purpose?

Yes, maybe best to just delete it.