Re: Differences in `ne` and `bp` line-breaking behavior

[Tadziu Hoffmann]

> Later in the same page we have this:
> [...]
> Does that cover the base in question?  The request synopses are
> supposed to be really terse, following the CSTR #54 model and
> serve as a refresher for the experienced.  The basic fact that
> moving the drawing position to (or past) a vertical position
> trap springs it is, I think, covered in the narrative above.

Certainly the behavior of traps is covered in the manual, I'm
just wondering whether traps will be on the reader's mind when
encountering that passage.  Even the authors of the Troff User's
Manual appear to think that it is worthwhile mentioning that .ne
could spring the trap.

I was thinking of something similar to

  .ne d    Advance drawing position to the next vertical
           position trap and spring the trap, if it is
           nearer than distance d (default scaling unit v).

but I'm not sure whether the use of a comma is grammatically
correct here.  The intent is to bind the two phrases joined
by "and" tighter than the two parts separated by the comma.
(Without the comma the "if" seems to bind tighter than the
"and".)  In an ideal world we could use parentheses for
grouping, like this:

  (advance position; spring trap) if distance < value