--- a/Float.st	Tue Dec 03 15:33:40 2019 +0100
+++ b/Float.st	Tue Dec 03 19:03:15 2019 +0100
@@ -124,8 +124,11 @@
  */
 # ifndef isnan
 #  define isnan(x)      \
-	((((unsigned int *)(&x))[0] == 0x00000000) && \
-	 (((unsigned int *)(&x))[1] == 0xFFF80000))
+	((((unsigned int *)(&x))[1] & 0x7F800000) == 0x7F800000)
+// old, invalid definition
+// #  define isnan(x)      \
+//         ((((unsigned int *)(&x))[0] == 0x00000000) && \
+//          (((unsigned int *)(&x))[1] == 0xFFF80000))
 # endif
 
 # ifndef isPositiveInfinity
@@ -693,22 +696,35 @@
 
     NaN isNil ifTrue:[
 %{
-#if defined(LINUX) && defined(__i386__)
-# ifdef NAN
-	@global(Float:NaN) = __MKFLOAT(NAN);
+#ifdef NAN
+        @global(Float:NaN) = __MKFLOAT(NAN);
+#else
+# if defined(LINUX) && defined(__i386__)
+        @global(Float:NaN) = __MKFLOAT(_SNAN);
 # else
-	@global(Float:NaN) = __MKFLOAT(_SNAN);
+#  if defined(__i386__) || defined(__x86_64__)
+        {
+            union {
+                double d;
+                int i[2];
+            } u;
+            u.i[0] = 0;
+            u.i[1] = 0x7FF80000;
+            @global(Float:NaN) = __MKFLOAT(u.d);
+        }
+#  endif
 # endif
 #endif
 %}.
-	NaN isNil ifTrue:[
-	    NaN := super NaN.
-	].
+        NaN isNil ifTrue:[
+            NaN := super NaN.
+        ].
     ].
     ^ NaN
 
-    "
+    "NaN := nil
      Float NaN
+     Float NaN negated
      Float NaN + 0.0
      Float NaN + Float NaN
      0.0 + Float NaN
@@ -3653,6 +3669,37 @@
     "
 !
 
+integerAndFractionParts
+    "return the integer and the fraction part of the receiver as a pair
+     of flaots (i.e. the result of the modf function)"
+
+    |integerPart fractionPart|
+
+%{
+#ifdef __SCHTEAM__
+    ERROR("unimplemented");
+#else
+    double dVal, iPart, fPart;
+    OBJ i, f;
+
+    dVal = __floatVal(self);
+    fPart = modf(dVal, &iPart);
+    __qMKFLOAT(i, iPart);
+    __qMKFLOAT(f, fPart);
+    integerPart = i;
+    fractionPart = f;
+#endif
+%}.
+    ^ { integerPart . fractionPart }
+
+    "
+     0.5 integerAndFractionParts
+     -0.5 integerAndFractionParts
+     12345.6789 integerAndFractionParts
+     -12345.6789 integerAndFractionParts
+    "
+!
+
 rounded
     "return the receiver rounded to the nearest integer"