symdiff produces unexpected results

[taylorwarczinsky]

Using symdiff with all the same types yields expected results

symdiff([1u"V", 2u"V", 3u"V"], [3u"V", 4u"V"])

yields

[1 V, 2 V, 4 V]

Changing one of the types breaks it

symdiff([1.0u"V", 2u"V", 3u"V"], [3u"V", 4u"V"])

yields

[1.0 V, 2.0 V, 3.0 V]

I'm not sure if the issue is related to julia base or unitful.jl. So I appologize if this is the wrong spot to post this issue. It seems like at minimum this should error out instead of returning incorrect results.

Unitful 1.27
Julia 1.11.7

[sostock]

That is because symdiff uses Set internally, which uses hashing, and hashing is broken for this package (#379). So it is in fact a problem with Unitful, not Julia.

Fixing hash for this particular case (where all units are the same) is easy. It is not so easy if you have different units (i.e., you would want symdiff([1V], [1000mV]) to be empty).

I will fix hash in the case of equal units soon (somehow I thought we had already done this).

[taylorwarczinsky]

Thanks for the update! I'll look forward to that fix. For now my work around is to convert my values to Float64 before using symdiff