SymbolicML/DynamicQuantities.jl

Beware of `preferunits`

j-fu opened this issue ยท 1 comments

j-fu commented

preferunits allows to change the preferred units such that they will deviate from the default SI base units:

julia> using DynamicQuantities, Unitful

julia> Unitful.preferunits(u"km")

julia> convert(DynamicQuantities.Quantity,3u"km")
3 ๐‹ ยน

I think users shall be made aware of this possibility.
In LessUnitful.jl I tried to provide an API function to allow a consistency check.

MilesCranmer commented

Thanks for the notice. The intention of upreferred was for instances like this to be a feature rather than a bug, so users could change the standardized form we convert to before performing calculations. But I just took a look and it seems like in fact due to how upreferred works, your example points out a bug:

julia> using DynamicQuantities, Unitful

julia> Unitful.preferunits(u"km")

julia> convert(DynamicQuantities.Quantity,3u"km")
3 ๐‹ ยน

julia> convert(Unitful.Quantity, convert(DynamicQuantities.Quantity,3u"km"))
3 m

So I guess upreferred should always be called within the conversion function, rather than to define a global conversion constant as is being done right now.

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