Extending setindex for vector indexing

[Micket]

Learning from my experiments on #745 i looked back at the missing support for vector indexing in setindex.

@inline function setindex(a::SVector{L}, v::AbstractArray, indices::AbstractArray) where L
    out = MVector(a)
    for (i, x) in zip(indices, v)
        # Do boundscheck here to allow Julia to fully elide the dynamic allocation.
        @boundscheck if (i < 1 || i > L)
            throw(BoundsError(a, i))
        end
        @inbounds out[i] = x
    end
    return SVector(out)
end

while we're at it, looks like setindex for scalars can easily be written this way as well.

@inline function setindex2(a::SVector{L}, x, index::Integer) where L
    out = MVector(a)
    # Do boundscheck here to allow Julia to fully elide the dynamic allocation.
    @boundscheck if (index < 1 || index > L)
        throw(BoundsError(a, index))
    end
    @inbounds out[index] = x
    return SVector(out)
end

Looking at assembly, it looks nicer for this implementation. I have had some mixed results trying to benchmark this; peaking at @code_native looked very efficient, but benchmark times still fell a bit short. Perhaps my benchmarks were lacking, or i missed something.

So is this interesting?

[andyferris]

It could be interesting. I had been waiting until the dust settles on non-scalar indexing in Julia where we may prefer a distinct generic function for non-scalar indexing (perhaps with syntax like a.[b] .= c) but there's no real reason to hold off too long...

Off topic... but do we really have an "arrays" label for StaticArrays? I'm amused. :)

[eschnett]

setindex should also support range indexing (via SUnitRange).