JuliaLang/julia
unary `+` acts differently for `Array` and `AbstractArray`
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#58.295 aperta il 1 mag 2025
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Descrizione
(This issue is tangentially related to #58281.)
The return type of unary + with Bool argument is not the same for arrays and views:
julia> v = [true, false]; +v
2-element Vector{Int64}:
1
0
julia> w = view(v, :); +w
2-element view(::Vector{Bool}, :) with eltype Bool:
1
0
The reason is that unary + for AbstractArray is simply the identity map:
Hence it misses the convention that + transforms Bool to Int.
Another consequence of this definition is that one doesn't know whether +v is identical to v for mutable v:
julia> v = [1, 2]; +v === v
false
julia> w = view(v, :); +w === w
true
In my opinion, it would be good to have a consistent answer. However, it may be to late for that.