shithub: neatroff

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cp: support conditional interpolation with \?'cond@expr1@expr2@'

This adds a new escape sequence for conditional interpolation: the
escape sequence \?'cond@expr1@expr2@', evaluates cond (exactly as if
it is a .if condition) and interpolates expr1, if the condition is
true, and expr2, otherwise.  The delimiter (@ in this example) can be
any character that cannot be part of the condition; for numerical
expressions, for instance, it cannot be a digit, an operator sign, or
a scale indicator, unless separated from the condition with \&.  The
final delimiter may be omitted.  Note that this escape sequence is not
interpolated in copy-mode.

--- a/char.c

+++ b/char.c

@@ -130,6 +130,16 @@

 	return ret;

 }

+/* like charnext_delim() for string buffers */

+int charread_delim(char **s, char *c, char *delim)

+{

+	int ret;

+	sstr_push(*s);

+	ret = charnext_delim(c, sstr_next, sstr_back, delim);

+	*s = sstr_pop();

+	return ret;

+}

+

 /* read the argument of a troff escape sequence */

 void argnext(char *d, int cmd, int (*next)(void), void (*back)(int))

 {

--- a/cp.c

+++ b/cp.c

@@ -34,6 +34,7 @@

 	return map(regname);

 }

+/* interpolate \n(xy */

 static void cp_num(void)

 {

 	int id;

@@ -47,6 +48,7 @@

 		in_push(num_str(id), NULL);

 }

+/* interpolate \*(xy */

 static void cp_str(void)

 {

 	char arg[ILNLEN];

@@ -68,11 +70,13 @@

 	}

 }

+/* interpolate \g(xy */

 static void cp_numfmt(void)

 {

 	in_push(num_getfmt(regid()), NULL);

 }

+/* interpolate \$1 */

 static void cp_arg(void)

 {

 	char argname[NMLEN];

@@ -86,6 +90,7 @@

 		in_push(arg, NULL);

 }

+/* interpolate \w'xyz' */

 static void cp_width(void)

 {

 	char wid[16];

@@ -93,6 +98,7 @@

 	in_push(wid, NULL);

 }

+/* define a register as \R'xyz expr' */

 static void cp_numdef(void)

 {

 	char arg[ILNLEN];

@@ -107,6 +113,33 @@

 	num_set(map(arg), eval_re(s, num_get(map(arg), 0), 'u'));

 }

+/* conditional interpolation as \?'cond@expr1@expr2@' */

+static void cp_cond(void)

+{

+	char arg[ILNLEN];

+	char delim[GNLEN], cs[GNLEN];

+	char *r, *s = arg;

+	char *s1, *s2;

+	int n;

+	argnext(arg, '?', cp_next, cp_back);

+	n = eval_up(&s, '\0');

+	if (charread(&s, delim) < 0)

+		return;

+	if (!strcmp(delim, "\\&") && charread(&s, delim) < 0)

+		return;

+	s1 = s;

+	r = s;

+	while (charread_delim(&s, cs, delim) >= 0)

+		r = s;

+	*r = '\0';

+	s2 = s;

+	r = s;

+	while (charread_delim(&s, cs, delim) >= 0)

+		r = s;

+	*r = '\0';

+	in_push(n > 0 ? s1 : s2, NULL);

+}

+

 static int cp_raw(void)

 {

 	int c;

@@ -176,6 +209,9 @@

 			c = cp_next();

 		} else if (c == 'R' && !cp_cpmode) {

 			cp_numdef();

+			c = cp_next();

+		} else if (c == '?' && !cp_cpmode) {

+			cp_cond();

 			c = cp_next();

 		} else {

 			cp_back(c);

--- a/roff.h

+++ b/roff.h

@@ -56,7 +56,7 @@

 #define SC_EM		(n_s * SC_IN / 72)

 /* escape sequences */

-#define ESC_Q	"bCDhHlLNoRSvwxX"	/* \X'ccc' quoted escape sequences */

+#define ESC_Q	"bCDhHlLNoRSvwxX?"	/* \X'ccc' quoted escape sequences */

 #define ESC_P	"*fgkmns"		/* \Xc \X(cc \X[ccc] escape sequences */

 #define MIN(a, b)	((a) < (b) ? (a) : (b))

@@ -391,6 +391,7 @@

 int charnext(char *c, int (*next)(void), void (*back)(int));

 int charread(char **s, char *c);

 int charnext_delim(char *c, int (*next)(void), void (*back)(int), char *delim);

+int charread_delim(char **s, char *c, char *delim);

 void charnext_str(char *d, char *c);

 void argnext(char *d, int cmd, int (*next)(void), void (*back)(int));

 void argread(char **sp, char *d, int cmd);