Better suggestion for replacement of [a]

[tomasaschan]

On Julia master:

julia> [1:5]
WARNING: [a] concatenation is deprecated; use [a;] instead
...

With this PR:

julia> [1:5]
WARNING: [a] concatenation is deprecated; use collect(a) instead
...

Ever since this was introduced, I've been silently annoyed by the suggestion to use [a;] - the syntax feels like a hack, and for users that aren't familiar with Julia already, it's far from obvious why there's a semi-colon there, and what the difference between [a] and [a;] is. However, I stayed silent, since I didn't have a better suggestion.

Now I do :)

I suggest we use collect(a) instead, for the following reasons:

• it's obvious what it does, much more so than [a;]
• it generalizes nicely when you want a different eltype, e.g. collect(Float64, 1:5)
• from what I understand of the discussion in WIP: Make [a, b] non-concatenating #8599 most of the opinions raised favored collect(a) over [a:] - not sure why it didn't happen. The only argument against collect was that it's slower (for UnitRanges, specifically), but Jeff quickly retorted that with "No problem, I will make collect faster."
• it just feels more Julian to me :)

I do realize that it doesn't generalize as nicely to higher dimensions, but since part of my problem with using ; in the 1D case is that it feels like something that belongs with multidimensional arrays, I don't really see that as an argument against this change.

[toivoh]

+1

[kmsquire]

👍

[tomasaschan]

In the long run, perhaps [a;] should also be deprecated to try to eradicate it from code bases out there, but I'm not sure it's so nice to be recommended an alternative syntax one day, just to have it deprecated the next... :P

[Jutho]

+1

[nolta]

Doesn't this print [collect(a)]?

[tomasaschan]

@nolta; good point, I'll fix that ASAP. Filed this from an edit on github mostly because I thought it was ridiculous too open an issue for such a small a change without making it a PR 😏

Still, it seems there is support for favoring collect(a) over [a;].

[ScottPJones]

👍

[prcastro]

👍

[garrison]

Was @nolta's point ever resolved?

[jakebolewski]

My bad, should be fixed.

[garrison]

thanks!

[tomasaschan]

@garrison, @jakebolewski No, I never got to fixing that. Was it fixed somewhere else, or should I submit a new patch to fix it?

[tkelman]

ec37d6d

[tomasaschan]

👍