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Re: [Bug-apl] Request for enhancement

From: Juergen Sauermann
Subject: Re: [Bug-apl] Request for enhancement
Date: Thu, 23 Jul 2015 18:55:27 +0200
User-agent: Mozilla/5.0 (X11; Linux i686; rv:31.0) Gecko/20100101 Thunderbird/31.4.0

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

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

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

/// 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

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