+# else
+ // any C++ header file undefines isinf and isnan
+ // so this should be included before <iostream>
+ // the functions are STILL in libm (libSystem on mac os x)
+extern "C" int (isnan)(double);
+extern "C" int (isinf)(double);
+# endif
+# else
+inline int (isnan)(double r) { return !(r <= 0 || r >= 0); }
+# endif
+#endif
+
+#if defined (__FreeBSD__)
+# if __FreeBSD_version < 500000
+ extern "C" {
+ inline int isnan(double r) { return !(r <= 0 || r >= 0); }
+ }
+# endif
+#endif
+
+#if defined (__CYGWIN__)
+# include <ieeefp.h> // isnan
+#endif