Guides/Boxdraw

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Box Draw Characters

J uses box drawing characters when displaying boxed data. Typically this requires a fixed pitch font.

The most portable way of drawing boxes is with the ascii characters +|- as below:

+---+---+----+
|abc|def|ghij|
+---+---+----|
|2  |3  |4   |
+---+---+----+

This displays predictably in all environments,  works in plain text email, and is the most portable form for communicating between users. When these aren't important and you have a suitable font you can use special box draw chars to provide crisper displays.

Box drawing with unicode J font characters is as below:

┌───┬───┬────┐
│abc│def│ghij│
├───┼───┼────┤
│2  │3  │4   │
└───┴───┴────┘

J draws boxes with 11 characters:

upper left corner     T down        upper right corner
T right               cross         T left
lower left corner     T up          lower right corner
vertical              horizontal

The values for the 11 characters can be queried with 9!:6 and set with 9!:7:

Box draw with J font chars is set with:

9!:7 [ (16+i.11){a.

Box draw with +|- is set with:

9!:7 '+++++++++|-'

Equivalently, call the utility boxdraw_j_:

boxdraw_j_ 0        NB. J font chars
boxdraw_j_ 1        NB. ascii font chars

The default boxdraw is set in the configuration files: base.cfg (jconsole and JHS) and qtide.cfg (Qt IDE).

Note that box draw can also use UTF-8 characters, e.g.

9!:7 [ 218 194 191 195 197 180 192 193 217 179 196{a.

J Engine input/output is in UTF-8 and the 9!:7 J font setting results in the Unicode values:

9484 9516 9488 9500 9532 9508 9492 9524 9496 9474 9472

Note: some unicode fixed pitch fonts do not have box draw characters of the same pitch and do not display well.