RFC: Show single column array as permutedims of single row

[simonbyrne]

The current matrix syntax has no elegant way for representing a matrix of a single column. Currently show (and repr) print elements separated by semicolons, which is actually parsed as a vector, e.g.

julia> x = [i for i=1:3, j=1:1]
3×1 Array{Int64,2}:
 1
 2
 3

julia> repr(x)
"[1; 2; 3]"

julia> eval(Meta.parse(repr(x)))
3-element Array{Int64,1}:
 1
 2
 3

This changes it so that it is represented as permutedims of a single row matrix:

julia> repr(x)
"permutedims([1 2 3])"

It's not the most elegant solution: feedback appreciated.

[simonbyrne]

Some other options:

• define a method Matrix(x::Vector), and print it as Matrix([1,2,3])
• define a function mat (analogous to vec), and print it as mat([1,2,3]).

[martinholters]

...or print as hcat([1,2,3]).

[simonbyrne]

hcat does look like the simplest option here.

[oxinabox]

Re the suggestion of mat, I like that one
I made (and abandonned) a PR for that a while ago
#23790

[simonbyrne]

Fixed by #33697