Re: Render \*(Pi as pi, not n

[Ingo Schwarze <schwarze@usta.de>]

Hi Ulrich,

Ulrich Spörlein wrote on Thu, Jun 02, 2011 at 01:15:47PM +0200:
> On Thu, 02.06.2011 at 12:54:56 +0300, Kristaps Dzonsons wrote:
>> On 02/06/2011 12:28, Ulrich Spörlein wrote:

>>> Hello,
>>>
>>> please consider doing the same as groff here, fixing ambiguities
>>>
>>> Before:
>>>
>>>       The atan2(), atan2f(), and atan2l() functions, if successful,
>>>       return the arc tangent of y/x in the range [-n, +n] radians.
>>>
>>> After:
>>>
>>>       The atan2(), atan2f(), and atan2l() functions, if successful,
>>>       return the arc tangent of y/x in the range [-pi, +pi] radians.
>>>
>>> Although 'n' might look a little like '??' we shouldn't replace random
>>> letters for greek symbols that have different meaning.

>> This is not something that groff agrees upon.  The stock groff on 
>> GNU/Linux returns `n' instead of `pi'.  Version: GNU troff (groff) 
>> version 1.21.  We've discussed this before, I think... the quick 
>> solution is to patch it downstream (chars.in).  I personally don't like 
>> the attenuation of /any/ Greek characters, as my own formulas end up 
>> confusing (those with both pi and n, for example).

> I disagree on groff disagreeing
> 
> FreeBSD base groff version 1.19.2: \*(Pi -> pi
> FreeBSD port groff version 1.21:   \*(Pi -> pi
> Ubuntu groff version 1.20.1:       \*(Pi -> pi

Oh that one, indeed.

I fixed this here and just need to merge it to bsd.lv:

http://www.openbsd.org/cgi-bin/cvsweb/src/usr.bin/mandoc/predefs.in
Revision 1.2

Ulrich is talking about \*(Pi in -Tascii,
Kristaps is talking about \(*p in -Tascii.

What groff does with \*(Pi is
 - "pi" in nroff mode (-Tascii)
 - real pi glyph in troff mode (-Tps)

Mandoc could do the same as long as it was handling predefined strings
in the same way as character escape sequences.  Now that it handles
predefined strings in the preprocessor, it cannot achieve this any
longer.

Hum.  I only realize now how serious that regression is from a
theoretical point of view...
Not sure what to do about this in general.

Yours,
  Ingo
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