allow == for two groups/group elements in fewer cases
#4196
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If `_check_compatible` for the two groups in question returns `false` then throw an exception. Note that the result is not based only on the types of the arguments but also on the groups.
src/Groups/GAPGroups.jl
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| @@ -372,9 +372,26 @@ end | |||
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| Base.:*(x::GAPGroupElem, y::GAPGroupElem) = _prod(x, y) | |||
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| ==(x::GAPGroup, y::GAPGroup) = GapObj(x) == GapObj(y) | |||
| function ==(x::GAPGroup, y::GAPGroup) | |||
| _check_compatible(x, y; error = false) || throw(ArgumentError("x and y are not compatible")) | |||
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| _check_compatible(x, y; error = false) || throw(ArgumentError("x and y are not compatible")) | |
| _check_compatible(x, y; error = true) |
wouldn't this be easier? (similar below)
I don't see a reason to first suppress an error and then throw basically the same one right afterwards
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Yes, we do not get a better error message in this case.
| # For two `GAPGroupElem`s, | ||
| # if no specialized method is applicable then no `==` comparison is allowed. | ||
| function ==(x::GAPGroupElem, y::GAPGroupElem) | ||
| _check_compatible(parent(x), parent(y); error = false) || throw(ArgumentError("parents of x and y are not compatible")) | ||
| throw(ArgumentError("== is not implemented for the given types")) | ||
| end |
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once Nemocas/AbstractAlgebra.jl#1853 is available, this method can be removed. maybe add this as a comment
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My point of view is:
If the compatibility check returns false then we are sure that the question for == is not allowed,
but if the compatibility check returns true then likely there is a new subtype of GAPGroupElem for which a == method should be provided.
(Currently we have just the subtypes BasicGAPGroupElem and MatrixGroupElem.)
| # For two `GAPGroupElem`s, | ||
| # if no specialized method is applicable then no `==` comparison is allowed. | ||
| function ==(x::GAPGroupElem, y::GAPGroupElem) | ||
| _check_compatible(parent(x), parent(y); error = false) || throw(ArgumentError("parents of x and y are not compatible")) |
If
_check_compatiblefor the two groups in question returnsfalsethen throw an exception.Note that the result is not based only on the types of the arguments but also on the groups.
This addresses one of the questions from #4191.