JuliaLang/julia
Document promotion behavior of `div` and `divrem` for `(::Unsigned, ::Signed)`
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#57,855 opened on 2025/03/21
docshelp wanted
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説明
Currently we have
julia> div(UInt(1), -1)
0xffffffffffffffff
This happens because we are returning the promote_type, but violates both common sense, and the documentation which states "Generally equivalent to a mathematical operation x/y without a fractional part".
As such, I propose that we instead make the return type of div(x,y) be ifelse(isa(y, Signed), signed(promote_type(x,y)), promote_type(x,y)). This would obviously be slightly breaking, but I think it qualifies as a bugfix.
We also would want to make similar changes for divrem, fld, cld since they all have the same problem.