@J.M.needshelp. Are you there?

Is it expected that JoinAcross[{<|"a" -> 1, "b" -> 2|>}, {}, "a", "Left"] gives {}? It seems a bit strange to me...

@yode I am now.

@J.M.needshelp. We are here

Hello everybody. Anyone knows the answer to this question? mathematica.stackexchange.com/questions/169977/…

I want to define a shortcut for a zero vector. Subscript[0, dim_] := Table[0, dim] seems to work and looks great, but it feels risky. Any thoughts?

Any potential side-effects from including in a package?

@ChrisK I'd prefer to attach this to a Symbol that isn't Subscript. Much safe. As a quick, probably not best, idea you could do: \[ScriptV]0 /: Subscript[\[ScriptV]0, n_] := ConstantArray[0, n]

The nice thing about this is if done at package level it won't harm anything outside of the package. The question at this point, though, is why not just do something like \[EmptySet][n_] := ConstantArray[0, n]?

Some easily identifiable character with nice alias. And just make it a function.

@b3m2a1 Yeah, you're right. Maybe I'll go for ZeroVector[dim], in loose analogy to IdentityMatrix. Thanks!

Anyone know how closely Mathematica's box-language follows the ideas of Knuth and Plass here? It seems to me like they ought to work in similar fashion, but I also know that Mathematica's mathematical typesetting is often seemingly lacking relative to TeX's.

@wesen Nope but here's a way to get started: mathematica.stackexchange.com/a/170016/38205