Allow Maybe{T} typealias

[Keno]

Jeff noted that

typealias Maybe{T} Union(T,Nothing)

and things like it can probably be easily implemented. Just noting it here, so we don't forget about it.

[toivoh]

+1

[ViralBShah]

+1

[amitmurthy]

+1

[bsxfan]

Has anyone ever thought of overloading | for types, so that one could use for example MyType | Nothing as a terse shortcut for Union(MyType,Nothing)?

[StefanKarpinski]

That has occurred to me many times but I was afraid of the wrath of Bezanson. Bezanson!! But seriously, it might be ok but we generally want to avoid a lot of puns on operators.

[Keno]

Note that that conflicts with using | as a piping operator (though we're probably gonna use |> anyway).

[quinnj]

I believe #5164 closes this?

[pao]

I'm not seeing the connection--do you mind spelling it out for my coffee-deprived brain?

[quinnj]

Hmmm.......I thought I remember seeing something about allowing any immutable as a type parameter, and thought this pull request did it, but perhaps it was more focused on just tuples. In any case, I ran the code at the top and it seems to work, so maybe this was closed by something else before?

[porterjamesj]

That PR was just about tuples. The code above worked fine before; it just wasn't (and still isn't) in Base.

[quinnj]

I guess I'm misunderstanding the purpose of this issue then. I thought it was because the above code wasn't legal (hence the "Allow this typealias..."). If it's just to include the Maybe{T} typealias in Base, then sorry for the noise.

[Keno]

No, I believe it originally didn't work. Seems to be fixed now.

[andrewcooke]

for people coming from googling "julia maybe type" - there's now Nullable which seems to be similar http://julia.readthedocs.org/en/latest/manual/types/#nullable-types-representing-missing-values