--- ray/src/common/calexpr.c	1993/03/05 15:14:00	2.12
+++ ray/src/common/calexpr.c	1995/02/16 09:49:29	2.16
@@ -34,10 +34,7 @@ static char SCCSid[] = "$SunId$ LBL";
 
 #define	 isdecimal(c)	(isdigit(c) || (c) == '.')
 
-#ifndef atof
-extern double  atof();
-#endif
-extern char  *fgets(), *savestr();
+extern char  *savestr();
 extern char  *emalloc(), *ecalloc();
 extern EPNODE  *curfunc;
 extern double  efunc(), evariable();
@@ -48,6 +45,10 @@ static double  echannel();
 static double  eadd(), esubtr(), emult(), edivi(), epow();
 static double  ebotch();
 
+#ifdef  DCL_ATOF
+extern double  atof();
+#endif
+
 int  nextc;				/* lookahead character */
 
 double	(*eoper[])() = {		/* expression operations */
@@ -125,6 +126,53 @@ char  *expr;
     rval = evalue(ep);
     epfree(ep);
     return(rval);
+}
+
+
+epcmp(ep1, ep2)			/* compare two expressions for equivalence */
+register EPNODE  *ep1, *ep2;
+{
+	double  d;
+
+	if (ep1->type != ep2->type)
+		return(1);
+
+	switch (ep1->type) {
+
+	case VAR:
+		return(ep1->v.ln != ep2->v.ln);
+
+	case NUM:
+		if (ep2->v.num == 0)
+			return(ep1->v.num != 0);
+		d = ep1->v.num / ep2->v.num;
+		return(d > 1.000000000001 | d < 0.999999999999);
+
+	case CHAN:
+	case ARG:
+		return(ep1->v.chan != ep2->v.chan);
+
+	case '=':
+	case ':':
+		return(epcmp(ep1->v.kid->sibling, ep2->v.kid->sibling));
+
+	case TICK:
+	case SYM:			/* should never get this one */
+		return(0);
+
+	default:
+		ep1 = ep1->v.kid;
+		ep2 = ep2->v.kid;
+		while (ep1 != NULL) {
+			if (ep2 == NULL)
+				return(1);
+			if (epcmp(ep1, ep2))
+				return(1);
+			ep1 = ep1->sibling;
+			ep2 = ep2->sibling;
+		}
+		return(ep2 != NULL);
+	}
 }