include/ngspice/cm.h, xspice, introduce NAN for visual studio

src/include/ngspice/cm.h

@@ -45,5 +45,16 @@ NON-STANDARD FEATURES
 #include "ngspice/cmproto.h"
 #include "ngspice/mifcmdat.h"
 
+#if defined (_MSC_VER)
+#ifndef NAN
+    static const __int64 global_nan = 0x7ff8000000000000i64;
+    #define NAN (*(const double *) &global_nan)
+#endif
+#endif
+
+#if !defined(NAN)
+#define NAN (0.0/0.0)
+#endif
+
 
 #endif

src/xspice/icm/xtradev/core/cfunc.mod

@@ -294,8 +294,8 @@ cm_core(ARGS)
             /*** must determine position progressively & then ***/
             /*** calculate required output. ***/
 
-            dout_din = 0.0 / 0.0;
-            B_out    = 0.0 / 0.0;
+            dout_din = NAN;
+            B_out    = NAN;
 
             for (i = 1; i < size; i++)
                 if (H_input < (H[i].rvalue + H[i+1].rvalue) / 2.0) {