JuliaArrays / JuliaArrays/StaticArrays.jl

Confusing display of zero-element SVector

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Julia
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Description

SVector{0, T}() displays in REPL as T[], indicating that it's the same object as if i created T[], even if the object itself is different:

julia> SVector{0, Float32}()
Float32[]

julia> about(Float32[])
0-element Vector{Float32} (mutable) (<: DenseVector{Float32} <: AbstractVector{Float32} <:Any), occupies 24B directly (referencing 40B in total, holding 0B of data)
  ref::MemoryRef{Float32} 16B «struct» MemoryRef{Float32}(Ptr{No … fb5a68cf5f0), Float32[])
 size::Tuple{Int64}        8B «struct» (0,)

 ■■■■■■■■■■■■■■■■■■■■■■■■■■■■■■■■■■■■■■■■■■■■■■■■
               16B                      8B       
 Float32 contents exist on the CPU within the ref::MemoryRef from 0x00007fb5a68cf5f0 to 0x00007fb5a68cf5f0.

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julia> about(SVector{0, Float32}())
0-element SVector{0, Float32} with indices SOneTo(0) (<: StaticArray{Tuple{0}, Float32, 1}<: AbstractVector{Float32} <: Any), occupies 0B.
singleton

julia> 

Otherwise SVectors display like this:

SVector(0.0)
1-element SVector{1, Float64} with indices SOneTo(1):
 0.0

So maybe the proper display for zero-element SVector would be something like:

SVector{0, T}()
0-element SVector{1, T} with indices SOneTo(0)

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Research direction

Reproduce the zero-element SVector and Vector outputs in the Julia REPL, then trace the display entry point used for SVector values. Done means the zero-element SVector is visibly distinguished from an ordinary T[] while non-empty SVector display remains unchanged.

Written by the indexing model from the issue text.

Assessment

Tech stack
julia
Domain
developer-experience
Issue type
Bug
Difficulty
3/5
Estimated time
1-2 days
Activity status
Active
Clarity
Mostly clear
Newbie friendliness
67/100

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