Julia 1.0 - Hackdot

Re:Julia 1.0 by Athas on Friday August 10, 2018 @03:37AM (#17731376)

> For example, the fact that an array of unions such as Array{Union{Missing,T}} is represented in memory as a much more efficient union of arrays is a perfect example of where a clever compiler can make the logical thing to do also the efficient thing to do!

Can you elaborate on how Julia represents arrays of unions, or point to some documentation? I'm working on something where an automatic efficient representation would be useful, and I'd like to learn from other's experience.

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Re:Julia 1.0 by iamed2 on Friday August 10, 2018 @04:36AM (#17731627)

There's an overview here: https://docs.julialang.org/en/v1.0.0/devdocs/isbitsunionarra...

In terms of the Julia changes that were needed to support this, there were two key PRs:

https://github.com/JuliaLang/julia/pull/20593 https://github.com/JuliaLang/julia/pull/22441

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Re:Julia 1.0 by Athas on Friday August 10, 2018 @05:34AM (#17731864)

Thanks, this looks about as I expected. The real problem occurs when you have an array of union types, where sum of the union cases are themselves way, which it does not look like Julia does anything clever about (because it's not even clear to me that it's even possible).

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