Hi maouinin,
I'll have a stab...
> > if \\nm=1 .X \\$@
>
> I follow the front, but what is \\$@?
From
.de Q
.if \\nm=1 .X \\$@
.if \\nm=2 .Y \\$@
.if \\nm=3 .Y \\$@
..
$@ refers to all the arguments passed to the macro, similar to $@ and $*
in sh. IOW, macro Q is calling either macro X or Y with all the
arguments it was passed. From groff's info page,
$ info groff 2>/dev/null |
> sed '/-- Escape: \\\$\*/p; 1,//d; /^$/Q'
-- Escape: \$*
-- Escape: \$@
In some cases it is convenient to use all of the arguments at once
(for example, to pass the arguments along to another macro). The
`\$*' escape concatenates all the arguments separated by spaces.
A similar escape is `\$@', which concatenates all the arguments
with each surrounded by double quotes, and separated by spaces.
If not in compatibility mode, the input level of double quotes is
preserved (see *note Request and Macro Arguments::).
$
> the following also loses me:
>
> > \h'\\nwu'\v'1m'\\*n\v'-1m'\h'\\nwu'\\$2
>
> what exactly is \\nwu?
\nw is the value of the w number register. The trailing u is stating
what units that number, e.g. 42, is in to \h for the horizontal
movement. If it was \nwi then it would be 42 inches instead. See
info groff 2>/dev/null | less +'/^[0-9.]* Measurements$'
In both cases, backslashes are doubled to delay interpretation to when
the macro is run, not defined.
Cheers, Ralph.
