Add some number operators for formats, from Tyler Culp.

Makefile

@@ -130,7 +130,7 @@ CDIAGFLAGS+= -Wundef -Wbad-function-cast -Winline -Wcast-align
 
 CFLAGS += -I${.CURDIR}
 
-LDADD=  -lutil -lcurses -levent
-DPADD=  ${LIBUTIL} ${LIBCURSES} ${LIBEVENT}
+LDADD=  -lutil -lcurses -levent -lm
+DPADD=  ${LIBUTIL} ${LIBCURSES} ${LIBEVENT} ${LIBM}
 
 .include <bsd.prog.mk>

format.c

@@ -23,6 +23,7 @@
 #include <errno.h>
 #include <fnmatch.h>
 #include <libgen.h>
+#include <math.h>
 #include <regex.h>
 #include <stdarg.h>
 #include <stdlib.h>
@@ -49,7 +50,6 @@ static void	 format_add_tv(struct format_tree *, const char *,
 		     struct timeval *);
 static int	 format_replace(struct format_tree *, const char *, size_t,
 		     char **, size_t *, size_t *);
-
 static void	 format_defaults_session(struct format_tree *,
 		     struct session *);
 static void	 format_defaults_client(struct format_tree *, struct client *);
@@ -1528,7 +1528,7 @@ format_build_modifiers(struct format_tree *ft, const char **s, u_int *count)
 		}
 
 		/* Now try single character with arguments. */
-		if (strchr("mCs=p", cp[0]) == NULL)
+		if (strchr("mCs=pe", cp[0]) == NULL)
 			break;
 		c = cp[0];
 
@@ -1784,6 +1784,108 @@ format_loop_panes(struct format_tree *ft, const char *fmt)
 	return (value);
 }
 
+static char *
+format_replace_expression(struct format_modifier *mexp, struct format_tree *ft,
+    const char *copy)
+{
+	int		 argc = mexp->argc;
+	const char	*errstr;
+	char		*endch, *value, *left = NULL, *right = NULL;
+	int		 use_fp = 0;
+	u_int		 prec = 0;
+	double		 mleft, mright, result;
+	enum { ADD, SUBTRACT, MULTIPLY, DIVIDE, MODULUS } operator;
+
+	if (strcmp(mexp->argv[0], "+") == 0)
+		operator = ADD;
+	else if (strcmp(mexp->argv[0], "-") == 0)
+		operator = SUBTRACT;
+	else if (strcmp(mexp->argv[0], "*") == 0)
+		operator = MULTIPLY;
+	else if (strcmp(mexp->argv[0], "/") == 0)
+		operator = DIVIDE;
+	else if (strcmp(mexp->argv[0], "%") == 0 ||
+	    strcmp(mexp->argv[0], "m") == 0)
+		operator = MODULUS;
+	else {
+		format_log(ft, "expression has no valid operator: '%s'",
+		    mexp->argv[0]);
+		goto fail;
+	}
+
+	/* The second argument may be flags. */
+	if (argc >= 2 && strchr(mexp->argv[1], 'f') != NULL) {
+		use_fp = 1;
+		prec = 2;
+	}
+
+	/* The third argument may be precision. */
+	if (argc >= 3) {
+		prec = strtonum(mexp->argv[2], INT_MIN, INT_MAX, &errstr);
+		if (errstr != NULL) {
+			format_log (ft, "expression precision %s: %s", errstr,
+			    mexp->argv[2]);
+			goto fail;
+		}
+	}
+
+	if (format_choose(ft, copy, &left, &right, 1) != 0) {
+		format_log(ft, "expression syntax error");
+		goto fail;
+	}
+
+	mleft = strtod(left, &endch);
+	if (*endch != '\0') {
+		format_log(ft, "expression left side is invalid: %s", left);
+		goto fail;
+	}
+
+	mright = strtod(right, &endch);
+	if (*endch != '\0') {
+		format_log(ft, "expression right side is invalid: %s", right);
+		goto fail;
+	}
+
+	if (!use_fp) {
+		mleft = (long long)mleft;
+		mright = (long long)mright;
+	}
+	format_log(ft, "expression left side is: %.*f", prec, mleft);
+	format_log(ft, "expression right side is:  %.*f", prec, mright);
+
+	switch (operator) {
+	case ADD:
+		result = mleft + mright;
+		break;
+	case SUBTRACT:
+		result = mleft - mright;
+		break;
+	case MULTIPLY:
+		result = mleft * mright;
+		break;
+	case DIVIDE:
+		result = mleft / mright;
+		break;
+	case MODULUS:
+		result = fmod(mleft, mright);
+		break;
+	}
+	if (use_fp)
+		xasprintf(&value, "%.*f", prec, result);
+	else
+		xasprintf(&value, "%.*f", prec, (double)(long long)result);
+	format_log(ft, "expression result is %s", value);
+
+	free(right);
+	free(left);
+	return value;
+
+fail:
+	free(right);
+	free(left);
+	return (NULL);
+}
+
 /* Replace a key. */
 static int
 format_replace(struct format_tree *ft, const char *key, size_t keylen,
@@ -1796,7 +1898,7 @@ format_replace(struct format_tree *ft, const char *key, size_t keylen,
 	size_t			  valuelen;
 	int			  modifiers = 0, limit = 0, width = 0, j;
 	struct format_modifier   *list, *fm, *cmp = NULL, *search = NULL;
-	struct format_modifier	**sub = NULL;
+	struct format_modifier	**sub = NULL, *mexp = NULL;
 	u_int			  i, count, nsub = 0;
 
 	/* Make a copy of the key. */
@@ -1848,6 +1950,11 @@ format_replace(struct format_tree *ft, const char *key, size_t keylen,
 				if (errptr != NULL)
 					width = 0;
 				break;
+			case 'e':
+				if (fm->argc < 1 || fm->argc > 3)
+					break;
+			    mexp = fm;
+				break;
 			case 'l':
 				modifiers |= FORMAT_LITERAL;
 				break;
@@ -2024,6 +2131,10 @@ format_replace(struct format_tree *ft, const char *key, size_t keylen,
 
 		free(condition);
 		free(found);
+	} else if (mexp != NULL) {
+		value = format_replace_expression(mexp, ft, copy);
+		if (value == NULL)
+			value = xstrdup("");
 	} else {
 		/* Neither: look up directly. */
 		value = format_find(ft, copy, modifiers);

tmux.1

@@ -4107,7 +4107,7 @@ specifies an
 .Xr fnmatch 3
 or regular expression comparison.
 The first argument is the pattern and the second the string to compare.
-An optional third argument specifies flags:
+An optional argument specifies flags:
 .Ql r
 means the pattern is a regular expression instead of the default
 .Xr fnmatch 3
@@ -4134,6 +4134,38 @@ ignores case.
 For example:
 .Ql #{C/r:^Start}
 .Pp
+Numeric operators may be performed by prefixing two comma-separated alternatives with an
+.Ql e
+and an operator.
+An optional
+.Ql f
+flag may be given after the operator to use floating point numbers, otherwise integers are used.
+This may be followed by a number giving the number of decimal places to use for the result.
+The available operators are:
+addition
+.Ql + ,
+subtraction
+.Ql - ,
+multiplication
+.Ql * ,
+division
+.Ql / ,
+and modulus
+.Ql m
+or
+.Ql %
+(note that
+.Ql %
+must be escaped as
+.Ql %%
+in formats which are also expanded by
+.Xr strftime 3 ) .
+For example,
+.Ql #{e|*|f|4:5.5,3}
+multiplies 5.5 by 3 for a result with four decimal places and
+.Ql #{e|%%:7,3}
+returns the modulus of 7 and 3.
+.Pp
 A limit may be placed on the length of the resultant string by prefixing it
 by an
 .Ql = ,

tmux.h

@@ -1822,6 +1822,7 @@ char		*paste_make_sample(struct paste_buffer *);
 #define FORMAT_PANE 0x80000000U
 #define FORMAT_WINDOW 0x40000000U
 struct format_tree;
+struct format_modifier;
 const char	*format_skip(const char *, const char *);
 int		 format_true(const char *);
 struct format_tree *format_create(struct client *, struct cmdq_item *, int,