--- ray/src/gen/genprism.c	1991/12/19 15:08:51	2.2
+++ ray/src/gen/genprism.c	1993/08/02 14:23:04	2.4
@@ -16,11 +16,13 @@ static char SCCSid[] = "$SunId$ LBL";
 
 #include  <stdio.h>
 
+#include  <math.h>
+
 #include  <ctype.h>
 
 #define  MAXVERT	1024		/* maximum # vertices */
 
-#ifndef atof
+#ifdef  DCL_ATOF
 extern double  atof();
 #endif