On 2024-08-08 07:16:03 -0500, G. Branden Robinson wrote:

At 2024-08-08T10:07:35+0200, Alejandro Colomar wrote:

quoted

Hmmm, I see.  Thanks!  I think "If x is ±0" is the clearest way to say
it.  I'm not sure if that glyph is available everywhere, though.  How
about "If x is 0 or -0"?

I think it's reasonable to assume that it's available.[1]  groff's
terminal output devices will either output it as-is or substitute a
fallback.

$ printf '±\n' | groff -K utf8 -T ascii | cat -s
+-

An argument could be made that this fallback should render "+/-"
instead.

With low-capability devices, there's often no single best answer to how
one should limp along.

FYI, +-0 could be interpreted by the reader as in C, where a unary
minus operator is applied, then a unary plus operator. And about +/-0,
the "/" is already used a the division operator, so that this doesn't
help parsing.

So ideally, the fallback for "±0" should be "+0 or -0", which is
much more readable and less ambiguous than "+-0" or "+/-0". But
this would imply the following:

In groff, of course, you can ask an output device whether it supports a
given glyph and define a string appropriately--but the first part of
that is not portable to formatters that don't implement groff
extensions, and doing so could rouse the ire of Ingo Schwarze's
mandoc(1).

Anyway, currently, for consistency, this should be "+0 or -0",
as this is already used:

cventin:~/software/man-pages> grep -r '\+0 or' man
man/man3/tgamma.3:Pole error: \fIx\fP is +0 or \-0
man/man3/tgamma.3:an argument of +0 or \-0 incorrectly produced a domain error
man/man3/pow.3:is +0 or \-0,
man/man3/pow.3:is +0 or \-0,
man/man3/atan2.3:is +0 or \-0, \-pi/2 is returned.
man/man3/atan2.3:is +0 or \-0, pi/2 is returned.
man/man3/cosh.3:is +0 or \-0, 1 is returned.
man/man3/erfc.3:is +0 or \-0, 1 is returned.

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