Use specified macro(NULL) instead of magic-number.

1 files changed, 3 insertions, 3 deletions

diff --git a/src/class.c b/src/class.c
index 5ea1f329f..2fa02fa87 100644
--- a/src/class.c
+++ b/src/class.c
@@ -128,7 +128,7 @@ mrb_class_outer_module(mrb_state *mrb, struct RClass *c)
   mrb_value outer;
 
   outer = mrb_obj_iv_get(mrb, (struct RObject*)c, mrb_intern_lit(mrb, "__outer__"));
-  if (mrb_nil_p(outer)) return 0;
+  if (mrb_nil_p(outer)) return NULL;
   return mrb_class_ptr(outer);
 }
 
@@ -1030,7 +1030,7 @@ mrb_method_search_vm(mrb_state *mrb, struct RClass **cp, mrb_sym mid)
     }
     c = c->super;
   }
-  return 0;                  /* no method */
+  return NULL;                  /* no method */
 }
 
 MRB_API struct RProc*
@@ -1295,7 +1295,7 @@ MRB_API struct RClass *
 mrb_class_real(struct RClass* cl)
 {
   if (cl == 0)
-    return 0;
+    return NULL;
   while ((cl->tt == MRB_TT_SCLASS) || (cl->tt == MRB_TT_ICLASS)) {
     cl = cl->super;
   }