--- ray/src/common/caldefn.c	1992/09/21 12:01:44	2.4
+++ ray/src/common/caldefn.c	1995/02/17 18:34:42	2.8
@@ -34,15 +34,15 @@ static char SCCSid[] = "$SunId$ LBL";
 #define	 NHASH		521		/* hash size (a prime!) */
 #endif
 
+#define  hash(s)	(shash(s)%NHASH)
+
 #define	 newnode()	(EPNODE *)ecalloc(1, sizeof(EPNODE))
 
 extern char  *ecalloc(), *emalloc(), *savestr(), *strcpy();
 
-static int  hash();
-
 static double  dvalue();
 
-long  eclock = -1;			/* value storage timer */
+unsigned long  eclock = 0;		/* value storage timer */
 
 static char  context[MAXWORD+1];	/* current context path */
 
@@ -189,14 +189,15 @@ register char  *ctx;
 
     if (ctx == NULL)
 	return(context);		/* just asking */
+    while (*ctx == CNTXMARK)
+	ctx++;				/* skip past marks */
     if (!*ctx) {
-	context[0] = '\0';		/* clear context */
+	context[0] = '\0';		/* empty means clear context */
 	return(context);
     }
-    cpp = context;			/* else copy it (carefully!) */
-    if (*ctx != CNTXMARK)
-	*cpp++ = CNTXMARK;		/* make sure there's a mark */
-    do {
+    cpp = context;			/* start context with mark */
+    *cpp++ = CNTXMARK;
+    do {				/* carefully copy new context */
 	if (cpp >= context+MAXWORD)
 	    break;			/* just copy what we can */
 	if (isid(*ctx))
@@ -205,12 +206,51 @@ register char  *ctx;
 	    *cpp++ = '_'; ctx++;
 	}
     } while (*ctx);
+    while (cpp[-1] == CNTXMARK)		/* cannot end in context mark */
+	cpp--;
     *cpp = '\0';
     return(context);
 }
 
 
 char *
+pushcontext(ctx)		/* push on another context */
+char  *ctx;
+{
+    extern char  *strncpy(), *strcpy();
+    char  oldcontext[MAXWORD+1];
+    register int  n;
+
+    strcpy(oldcontext, context);	/* save old context */
+    setcontext(ctx);			/* set new context */
+    n = strlen(context);		/* tack on old */
+    if (n+strlen(oldcontext) > MAXWORD) {
+	strncpy(context+n, oldcontext, MAXWORD-n);
+	context[MAXWORD] = '\0';
+    } else
+	strcpy(context+n, oldcontext);
+    return(context);
+}
+
+
+char *
+popcontext()			/* pop off top context */
+{
+    register char  *cp1, *cp2;
+
+    if (!context[0])			/* nothing left to pop */
+	return(context);
+    cp2 = context;			/* find mark */
+    while (*++cp2 && *cp2 != CNTXMARK)
+	;
+    cp1 = context;			/* copy tail to front */
+    while (*cp1++ = *cp2++)
+	;
+    return(context);
+}
+
+
+char *
 qualname(nam, lvl)		/* get qualified name */
 register char  *nam;
 int  lvl;
@@ -516,7 +556,7 @@ getstatement()			/* get next statement */
 	qname = qualname(dname(ep), 0);
 #ifdef	REDEFW
 	if ((vdef = varlookup(qname)) != NULL)
-	    if (vdef->def != NULL) {
+	    if (vdef->def != NULL && epcmp(ep, vdef->def)) {
 		wputs(qname);
 		if (vdef->def->type == ':')
 		    wputs(": redefined constant expression\n");
@@ -598,7 +638,7 @@ getdefn()			/* A -> SYM = E1 */
 	    ep1->sibling->type != NUM) {
 	ep1 = newnode();
 	ep1->type = TICK;
-	ep1->v.tick = -1;
+	ep1->v.tick = 0;
 	addekid(ep2, ep1);
 	ep1 = newnode();
 	ep1->type = NUM;
@@ -659,25 +699,12 @@ EPNODE	*d;
     if (ep1->type == NUM)
 	return(ep1->v.num);			/* return if number */
     ep2 = ep1->sibling;				/* check time */
-    if (ep2->v.tick < 0 || ep2->v.tick < eclock) {
-	ep2->v.tick = d->type == ':' ? 1L<<30 : eclock;
+    if (ep2->v.tick == 0 || ep2->v.tick < eclock) {
+	ep2->v.tick = d->type == ':' ? ~0L : eclock;
 	ep2 = ep2->sibling;
 	ep2->v.num = evalue(ep1);		/* needs new value */
     } else
 	ep2 = ep2->sibling;			/* else reuse old value */
 
     return(ep2->v.num);
-}
-
-
-static int
-hash(s)				/* hash a string */
-register char  *s;
-{
-    register int  rval = 0;
-
-    while (*s)
-	rval += *s++;
-    
-    return(rval % NHASH);
 }