Compact printing of Array{Char}s?

[andreasnoack]

@alanedelman brought up that Array{Char}s can be useful for summarizing numerical arrays but that it would be better if the printing of Array{Char} was more compact. I.e. instead of

julia> A = randn(10,10);

julia> ['+', '-'][(A .> 0) + 1]
10×10 Array{Char,2}:
 '+'  '-'  '-'  '-'  '-'  '-'  '-'  '+'  '+'  '-'
 '-'  '-'  '-'  '-'  '-'  '+'  '-'  '+'  '+'  '+'
 '-'  '+'  '+'  '+'  '+'  '+'  '-'  '-'  '-'  '+'
 '-'  '+'  '-'  '+'  '-'  '+'  '-'  '+'  '+'  '-'
 '-'  '-'  '+'  '+'  '-'  '-'  '-'  '-'  '+'  '-'
 '-'  '-'  '+'  '+'  '-'  '+'  '+'  '-'  '-'  '-'
 '+'  '-'  '+'  '+'  '-'  '+'  '+'  '-'  '+'  '-'
 '-'  '-'  '-'  '+'  '+'  '-'  '+'  '-'  '-'  '-'
 '-'  '-'  '-'  '-'  '+'  '+'  '-'  '-'  '+'  '-'
 '-'  '-'  '+'  '+'  '-'  '+'  '+'  '-'  '+'  '-'

it was proposed that we follow our competitor and print it like

julia> print(join(mapslices(String, ['+', '-'][(A .> 0) + 1], 2), '\n'))
+------++-
-----+-+++
-+++++---+
-+-+-+-++-
--++----+-
--++-++---
+-++-++-+-
---++-+---
----++--+-
--++-++-+-

Thoughts?

[stevengj]

That works well if all the chars have charwidth(c) == 1, but it seems problematic in other cases.

Also is a bit problematic if you have a lot of whitespace chars.

[andreasnoack]

Would it make sense to adjust the width of each "cell" to the maximum charwidth of the array? There seems to be something wrong with wide characters in the mac terminals, though, so I don't know if it is yet possible to make special characters look good in the terminal.

[stevengj]

@andreasnoack, that's #3721. It seems to be really hard to solve unless the whole software stack (terminal on up) agrees on the width of the characters.

[stevengj]

Also, charwidth-0 characters (e.g. combining characters) are going to look odd.

[TotalVerb]

@stevengj combining characters already print odd (they combine with the initial single quote), so that will not be a new issue.

[oscardssmith]

given variable width chars, this is probably a bad idea.