Re: [Bug-apl] Request for enhancement

[Juergen Sauermann]

Hi Fred,

not sure what you mean by I would like to request three additional UTF-8 characters to be added.

GNU APL supports the entire Unicode character set to the extent that your platform supports
(= is able to display) it. So you can't actually add characters to GNU APL. For example,
overline (UTF-8 E2 80 BE = U+203E = 8254 decimal) can be printed as using ⎕UCS and
also entered directly into string constants

      ⎕UCS 8254    ⍝ print overline
‾

      ⎕UCS '‾'   ⍝ use overline in string constants
8254

However, the characters you mentioned are not in the ⎕AV of GNU APL (and they do not
have to be in ⎕AV in order to use them!).  The reason is that for several compatibility reasons
⎕AV has 256 characters.  If you add new ones then we have to kill old ones. My strategy is
to keep ⎕AV changes to a minimum. The only valid reason for adding characters to ⎕AV is
when a new character with APL significance is needed and the new character is not in ⎕AV.
Not adding such a character would break some exhange formats which are ⎕AV based. In
short, this means that the characters in the current ⎕AV of GNU APL that have no APL
relevance are the candidates for removal when new characters with APL relevance need to
be added. The last case where this happend was ⍬ (zilde) if I remember correctly.

Regarding the overlined characters. I believe this is also already working in GNU APL if your
terminal supports combining chars. For example, on my xterm:

      ('0', ⎕UCS 773),('1', ⎕UCS 773)   ⍝ print 0 and 1 overlined
0̅1̅

prints 0 and 1 overlined. The trick is the Unicode page called Combining Diacritical Marks
(U+0300 ... U+03FF) which contains numerous characters that can be combined with regular
ones.

/// Jürgen

On 07/23/2015 05:59 PM, Fred Weigel wrote:

The current definition of letter includes a..z and A..Z, _, del, high
minus and underscored del.

I would like to request three additional UTF-8 characters to be added:

Overline E2 80 BE (UTF-8), complementary to _ (underline)

Combining underline CC B2 (UTF-8) -- if this follows a letter, the
letter is rendered with an underline.

Combining overline CC 85 (UTF-8)-- if this follows a letter, the letter
is rendered with an overline.

As well, I would like combining overline to be included in the
definition of numeric digit: this can be used to mark digits as
repeating in code: 0.3(overbar) could be expanded to 0.33.. (as many as
needed to fill the precision). 2.1(overbar)2(overbar) should become
2.121212... (as many as needed).

Of course, I am be insane (my mother never had me tested).

Fred Weigel