I wrote:
> $ echo '\[-+]' | nroff | grep .
> ∓
> $ echo '\[-+]' | nroff -Tascii | grep .
> -+
> $ echo '\[-+]' | nroff -Tiso-8859-1 | grep .
> ∓
> $
I made a mistake with `nroff -Tiso-8859-1'; that's not a valid -T
value. nroff(1) says
If neither the GROFF_TYPESETTER environment variable nor the -T
command line option (which overrides the environment variable)
specifies a (valid) device, nroff checks the current locale to
select a default output device.
Why is it useful to have nroff ignore a duff -T value and fall back as
if it was unspecified?
Switching to the valid equivalent(?):
$ echo '\[-+]' | nroff -Tlatin1 | grep .
-+
$
latin1(7) here says
Oct Dec Hex Char Description
───────────────────────────────────────────
...
261 177 B1 ± PLUS-MINUS SIGN
and that seems defined in the device's fonts
$ fgrep +- font/devlatin1/R
+- 24 0 0261
t+- "
$
so why isn't grotty outputing the single byte for it?
> I'm guessing it's to do with the type of output you're producing.
As Carsten's said.
$ echo '\[-+]' | groff >/dev/null
<standard input>:1: warning: can't find special character `-+'
$
The PostScript glyph name is `plusminus'.
$ curl -sS
http://partners.adobe.com/public/developer/en/opentype/glyphlist.txt |
> grep plusminus
plusminus;00B1
$
It's used in the Times Roman font definition.
$ grep plusminus font/devps/TR
t+- 564,506 0 177 plusminus
$
But for some reason, it's called `t+-'. Using that works, with the
appropriate single byte being printed.
$ echo '\[t+-]' | groff | grep /F0
/F0 10/Times-Roman@0 SF<b1>72 12 Q 0 Cg EP
$ echo $((0xb1))
177
$
Why it's not known as \[+-] too, I don't know.
So, I haven't answered the "whys". Someone else can, I'm sure. :-)
Cheers, Ralph.
