__END_NAMESPACE_C99
#endif
-
-/* Return nonzero if VALUE is not a number. */
-/* DELETE? __MATHDECL_PRIV adds another "__": so this is "____isnan"???! */
-/*__MATHDECL_PRIV (int,__isnan,, (_Mdouble_ __value), (__const__))*/
-
-#if defined __USE_MISC || defined __USE_XOPEN
+#if defined __USE_MISC || defined __USE_XOPEN || defined __USE_ISOC99
/* Return nonzero if VALUE is not a number. */
+__BEGIN_NAMESPACE_C99
__MATHDECL_PRIV (int,isnan,, (_Mdouble_ __value), (__const__))
+__END_NAMESPACE_C99
+#endif
+#if defined __USE_MISC || defined __USE_XOPEN
# ifdef __DO_XSI_MATH__
/* Bessel functions. */
__MATHCALL (j0,, (_Mdouble_))