Changed meaning of .+= in Julia 0.5

[stevengj]

Your test code uses x .+= y, so you should know that in Julia 0.5 this has changed meaning to be equivalent to broadcast!(identity, x, x .+ y), so that it mutates the x array (see JuliaLang/julia#17510 … in Julia 0.6 the whole operation will occur in-place without temporaries). So .+ should only be used if the left-hand side is a mutable array, and you don't mind mutating it.

At first glance, this looks like it is okay for you, because you use it in rgb[:g,:] .+= 1, where rgb[:g,:] is an array that you are mutating anyway. But if it were a problem you could always change it to +=.

[SimonDanisch]

That's really great news! Thanks for the heads up!

[stevengj]

Feel free to close if your code is okay. However, as I just noticed in JuliaLang/julia#17510, because rgb[:g,:] returns a copy and not a view, I think this may be broken until I can fix the .= to use view for left-hand-side getindex expressions; for now, you can do rgb[:g,:] = rgb[:g,:] .+ 1

[c42f]

Yes, thanks for letting us know, lately I've been getting used to 0.5-dev breaking FixedSizeArrays without warning ;-)

In the tests, the expression @fslice rgb[:g,:] .+= 1 is being rewritten by @fslice into

destructure(rgb)[fieldindex(eltype(rgb),:g), :] .+= 1

which should use a view in broadcast as it updates rgb in place. However, I don't think this is a critical feature since I only just updated @fslice to allow opassign syntax recently. I'm fine with just waiting until the fix lands in 0.5 and testing then.

[stevengj]

It should be fixed in JuliaLang/julia#17546 to call view, although I'm not sure whether that will fix @fslice. Does view(destructure(rgb), fieldindex(eltype(rgb),:g), :) work?

[c42f]

Thanks @stevengj I just checked your branch, and @fslice works fine there. (destructure() simply reinterprets an Array{T<:FixedArray} as a higher dimensional Array with the fixed dimensions prepended to the original size, so anything which works with a normal array should work with the result of a destructure().)