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-rw-r--r--libguile/feature.h5
1 files changed, 4 insertions, 1 deletions
diff --git a/libguile/feature.h b/libguile/feature.h
index aa61c740f..8ba59891b 100644
--- a/libguile/feature.h
+++ b/libguile/feature.h
@@ -42,11 +42,14 @@
* If you write modifications of your own for GUILE, it is your choice
* whether to permit this exception to apply to your modifications.
* If you do not wish that, delete this exception notice. */
+
+/* Software engineering face-lift by Greg J. Badros, 11-Dec-1999,
+ gjb@cs.washington.edu, http://www.cs.washington.edu/homes/gjb */
#include "libguile/__scm.h"
-#define SCM_HOOKP(x) (SCM_TYP16 (x) == scm_tc16_hook)
+#define SCM_HOOKP(x) (SCM_NIMP(x) && (SCM_TYP16 (x) == scm_tc16_hook))
#define SCM_HOOK_ARITY(hook) (SCM_CAR (hook) >> 16)
#define SCM_HOOK_NAME(hook) SCM_CADR (hook)
#define SCM_HOOK_PROCEDURES(hook) SCM_CDDR (hook)