minor

Author: dance858

src/bivariate/multiply.c

@@ -27,7 +27,7 @@ static void jacobian_init(expr *node)
 {
     /* if a child is a variable we initialize its jacobian for a
        short chain rule implementation */
-    if (node->left->var_id != -1)
+    if (node->left->var_id != NOT_A_VARIABLE)
     {
         node->left->jacobian_init(node->left);
     }

src/bivariate/rel_entr.c

@@ -2,6 +2,7 @@
 #include <assert.h>
 #include <math.h>
 #include <stdlib.h>
+#include <string.h>
 
 // --------------------------------------------------------------------
 // Implementation of relative entropy when both arguments are vectors.