-.\" $Id: roff.7,v 1.95 2017/12/15 23:39:07 schwarze Exp $
+.\" $Id: roff.7,v 1.96 2018/04/10 00:52:30 schwarze Exp $
.\"
.\" Copyright (c) 2010, 2011, 2012 Kristaps Dzonsons <kristaps@bsd.lv>
-.\" Copyright (c) 2010,2011,2013-2015,2017 Ingo Schwarze <schwarze@openbsd.org>
+.\" Copyright (c) 2010-2018 Ingo Schwarze <schwarze@openbsd.org>
.\"
.\" Permission to use, copy, modify, and distribute this software for any
.\" purpose with or without fee is hereby granted, provided that the above
.\" ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
.\" OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
.\"
-.Dd $Mdocdate: December 15 2017 $
+.Dd $Mdocdate: April 10 2018 $
.Dt ROFF 7
.Os
.Sh NAME
.It Ic \&nop Ar body
Execute the rest of the input line as a request or macro line.
Currently unsupported.
-.It Ic \&nr Ar register Oo Cm + Ns | Ns Cm - Oc Ns Ar expression
+.It Ic \&nr Ar register Oo Cm + Ns | Ns Cm - Oc Ns Ar expression Op Ar stepsize
Define or change a register.
A register is an arbitrary string value that defines some sort of state,
which influences parsing and/or formatting.
If it is prefixed by a sign, the register will be
incremented or decremented instead of assigned to.
.Pp
+The
+.Ar stepsize
+is used by the
+.Ic \en+
+auto-increment feature.
+It remains unchanged when omitted while changing an existing register,
+and it defaults to 0 when defining a new register.
+.Pp
The following
.Ar register
is handled specially:
Character
.Ar number
on the current font.
-.Ss \en Ns Bq Ar name
+.Ss \en Ns Oo +|- Oc Ns Bq Ar name
Interpolate the number register
.Ar name .
For short names, there are variants
.No \en Ns Ar c
and
.No \en( Ns Ar cc .
+If the optional sign is specified,
+the register is first incremented or decremented by the
+.Ar stepsize
+that was specified in the relevant
+.Ic \&nr
+request, and the changed value is interpolated.
.Ss \eo\(aq Ns Ar string Ns \(aq
Overstrike, writing all the characters contained in the
.Ar string