Two new low-level roff(7) features:

* .nr optional third argument (auto-increment step size)
* \n+ and \n- numerical register auto-increment and -decrement
bentley@ reported on Dec 9, 2013 that lang/sbcl(1) uses these.

6 files changed, 110 insertions, 26 deletions

diff --git a/TODO b/TODO
index 3055df6d..ccfd625d 100644
--- a/TODO
+++ b/TODO
@@ -52,10 +52,6 @@ are mere guesses, and some may be wrong.
   found by naddy@ in xloadimage(1)
   loc **  exist ***  algo *  size *  imp *
 
-- .nr third argument (auto-increment step size, requires \n+)
-  found by bentley@ in sbcl(1)  Mon, 9 Dec 2013 18:36:57 -0700
-  loc *  exist *  algo *  size *  imp **
-
 - .ns (no-space mode) occurs in xine-config(1)
   when implementing this, also let .TH set it
   reported by brad@  Sat, 15 Jan 2011 15:45:23 -0500
@@ -65,10 +61,6 @@ are mere guesses, and some may be wrong.
   found by jca@ in ratpoison(1)  Sun, 30 Jun 2013 12:01:09 +0200
   loc *  exist **  algo **  size **  imp **
 
-- \n+ and \n- numerical register increment and decrement
-  found by bentley@ in sbcl(1)  Mon, 9 Dec 2013 18:36:57 -0700
-  loc *  exist *  algo *  size *  imp **
-
 - \w'' improve width measurements
   would not be very useful without an expression parser, see below
   needed for Tcl_NewStringObj(3) via wiz@  Wed, 5 Mar 2014 22:27:43 +0100
diff --git a/regress/roff/nr/Makefile b/regress/roff/nr/Makefile
index b3ba8102..562a5f30 100644
--- a/regress/roff/nr/Makefile
+++ b/regress/roff/nr/Makefile
@@ -1,6 +1,6 @@
 # $OpenBSD: Makefile,v 1.9 2015/01/23 00:38:43 schwarze Exp $
 
-REGRESS_TARGETS = argc divzero escname eval int predef rr scale undef
+REGRESS_TARGETS = argc divzero escname eval incr int predef rr scale undef
 LINT_TARGETS	= divzero escname
 
 .include <bsd.regress.mk>
diff --git a/regress/roff/nr/incr.in b/regress/roff/nr/incr.in
new file mode 100644
index 00000000..a03493ff
--- /dev/null
+++ b/regress/roff/nr/incr.in
@@ -0,0 +1,30 @@
+.\" $OpenBSD: undef.in,v 1.1 2018/04/09 22:26:25 schwarze Exp $
+.TH NR-INCR 1 "April 10, 2018"
+.SH NAME
+nr-incr \- increment a number register by accessing it
+.SH DESCRIPTION
+.nr myr 0 1
+Roff can count by merely accessing a number register:
+\n+[myr]
+\n+[myr]
+\n+[myr]
+.PP
+.nr myr +0 1+1
+It can also change the step size:
+\n+[myr]
+\n+[myr]
+\n+[myr]
+.PP
+.nr myr +0 3
+It can also count down:
+\n-[myr]
+\n-[myr]
+\n-[myr]
+\n-[myr]
+.PP
+.nr myr -0 -2
+Down in negative steps is up:
+\n-[myr]
+\n-[myr]
+\n-[myr]
+\n-[myr]
diff --git a/regress/roff/nr/incr.out_ascii b/regress/roff/nr/incr.out_ascii
new file mode 100644
index 00000000..d039d5b1
--- /dev/null
+++ b/regress/roff/nr/incr.out_ascii
@@ -0,0 +1,19 @@
+NR-INCR(1)                  General Commands Manual                 NR-INCR(1)
+
+
+
+NNAAMMEE
+       nr-incr - increment a number register by accessing it
+
+DDEESSCCRRIIPPTTIIOONN
+       Roff can count by merely accessing a number register: 1 2 3
+
+       It can also change the step size: 5 7 9
+
+       It can also count down: 6 3 0 -3
+
+       Down in negative steps is up: -1 1 3 5
+
+
+
+OpenBSD                         April 10, 2018                      NR-INCR(1)
diff --git a/roff.7 b/roff.7
index 2b9053e4..b7f499d9 100644
--- a/roff.7
+++ b/roff.7
@@ -1,7 +1,7 @@
 .\"	$Id$
 .\"
 .\" 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
@@ -1348,7 +1348,7 @@ Currently unsupported.
 .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.
@@ -1360,6 +1360,14 @@ below.
 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:
@@ -1996,13 +2004,19 @@ and
 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
diff --git a/roff.c b/roff.c
index e85961b6..d820ee15 100644
--- a/roff.c
+++ b/roff.c
@@ -73,6 +73,7 @@ struct	roffkv {
 struct	roffreg {
 	struct roffstr	 key;
 	int		 val;
+	int		 step;
 	struct roffreg	*next;
 };
 
@@ -182,7 +183,8 @@ static	void		 roff_freestr(struct roffkv *);
 static	size_t		 roff_getname(struct roff *, char **, int, int);
 static	int		 roff_getnum(const char *, int *, int *, int);
 static	int		 roff_getop(const char *, int *, char *);
-static	int		 roff_getregn(struct roff *, const char *, size_t);
+static	int		 roff_getregn(struct roff *,
+				const char *, size_t, char);
 static	int		 roff_getregro(const struct roff *,
 				const char *name);
 static	const char	*roff_getstrn(struct roff *,
@@ -207,7 +209,7 @@ static	enum rofferr	 roff_rm(ROFF_ARGS);
 static	enum rofferr	 roff_rn(ROFF_ARGS);
 static	enum rofferr	 roff_rr(ROFF_ARGS);
 static	void		 roff_setregn(struct roff *, const char *,
-				size_t, int, char);
+				size_t, int, char, int);
 static	void		 roff_setstr(struct roff *,
 				const char *, const char *, int);
 static	void		 roff_setstrn(struct roffkv **, const char *,
@@ -1136,6 +1138,7 @@ roff_res(struct roff *r, struct buf *buf, int ln, int pos)
 	int		 done;	/* no more input available */
 	int		 deftype; /* type of definition to paste */
 	int		 rcsid;	/* kind of RCS id seen */
+	char		 sign;	/* increment number register */
 	char		 term;	/* character terminating the escape */
 
 	/* Search forward for comments. */
@@ -1246,6 +1249,9 @@ roff_res(struct roff *r, struct buf *buf, int ln, int pos)
 			term = cp[1];
 			/* FALLTHROUGH */
 		case 'n':
+			sign = cp[1];
+			if (sign == '+' || sign == '-')
+				cp++;
 			res = ubuf;
 			break;
 		default:
@@ -1350,7 +1356,7 @@ roff_res(struct roff *r, struct buf *buf, int ln, int pos)
 		case 'n':
 			if (arg_complete)
 				(void)snprintf(ubuf, sizeof(ubuf), "%d",
-				    roff_getregn(r, stnam, naml));
+				    roff_getregn(r, stnam, naml, sign));
 			else
 				ubuf[0] = '\0';
 			break;
@@ -2522,12 +2528,12 @@ roff_evalnum(struct roff *r, int ln, const char *v,
 void
 roff_setreg(struct roff *r, const char *name, int val, char sign)
 {
-	roff_setregn(r, name, strlen(name), val, sign);
+	roff_setregn(r, name, strlen(name), val, sign, INT_MIN);
 }
 
 static void
 roff_setregn(struct roff *r, const char *name, size_t len,
-    int val, char sign)
+    int val, char sign, int step)
 {
 	struct roffreg	*reg;
 
@@ -2544,6 +2550,7 @@ roff_setregn(struct roff *r, const char *name, size_t len,
 		reg->key.p = mandoc_strndup(name, len);
 		reg->key.sz = len;
 		reg->val = 0;
+		reg->step = 0;
 		reg->next = r->regtab;
 		r->regtab = reg;
 	}
@@ -2554,6 +2561,8 @@ roff_setregn(struct roff *r, const char *name, size_t len,
 		reg->val -= val;
 	else
 		reg->val = val;
+	if (step != INT_MIN)
+		reg->step = step;
 }
 
 /*
@@ -2589,11 +2598,11 @@ roff_getregro(const struct roff *r, const char *name)
 int
 roff_getreg(struct roff *r, const char *name)
 {
-	return roff_getregn(r, name, strlen(name));
+	return roff_getregn(r, name, strlen(name), '\0');
 }
 
 static int
-roff_getregn(struct roff *r, const char *name, size_t len)
+roff_getregn(struct roff *r, const char *name, size_t len, char sign)
 {
 	struct roffreg	*reg;
 	int		 val;
@@ -2604,12 +2613,24 @@ roff_getregn(struct roff *r, const char *name, size_t len)
 			return val;
 	}
 
-	for (reg = r->regtab; reg; reg = reg->next)
+	for (reg = r->regtab; reg; reg = reg->next) {
 		if (len == reg->key.sz &&
-		    0 == strncmp(name, reg->key.p, len))
+		    0 == strncmp(name, reg->key.p, len)) {
+			switch (sign) {
+			case '+':
+				reg->val += reg->step;
+				break;
+			case '-':
+				reg->val -= reg->step;
+				break;
+			default:
+				break;
+			}
 			return reg->val;
+		}
+	}
 
-	roff_setregn(r, name, len, 0, '\0');
+	roff_setregn(r, name, len, 0, '\0', INT_MIN);
 	return 0;
 }
 
@@ -2649,9 +2670,9 @@ roff_freereg(struct roffreg *reg)
 static enum rofferr
 roff_nr(ROFF_ARGS)
 {
-	char		*key, *val;
+	char		*key, *val, *step;
 	size_t		 keysz;
-	int		 iv;
+	int		 iv, is, len;
 	char		 sign;
 
 	key = val = buf->buf + pos;
@@ -2666,9 +2687,17 @@ roff_nr(ROFF_ARGS)
 	if (sign == '+' || sign == '-')
 		val++;
 
-	if (roff_evalnum(r, ln, val, NULL, &iv, ROFFNUM_SCALE))
-		roff_setregn(r, key, keysz, iv, sign);
+	len = 0;
+	if (roff_evalnum(r, ln, val, &len, &iv, ROFFNUM_SCALE) == 0)
+		return ROFF_IGN;
+
+	step = val + len;
+	while (isspace((unsigned char)*step))
+		step++;
+	if (roff_evalnum(r, ln, step, NULL, &is, 0) == 0)
+		is = INT_MIN;
 
+	roff_setregn(r, key, keysz, iv, sign, is);
 	return ROFF_IGN;
 }