add numerical recipes library

lib/nr/k_and_r/recipes/ran0.c

@@ -0,0 +1,28 @@
+
+#define IA 16807
+#define IM 2147483647
+#define AM (1.0/IM)
+#define IQ 127773
+#define IR 2836
+#define MASK 123459876
+
+float ran0(idum)
+long *idum;
+{
+	long k;
+	float ans;
+
+	*idum ^= MASK;
+	k=(*idum)/IQ;
+	*idum=IA*(*idum-k*IQ)-IR*k;
+	if (*idum < 0) *idum += IM;
+	ans=AM*(*idum);
+	*idum ^= MASK;
+	return ans;
+}
+#undef IA
+#undef IM
+#undef AM
+#undef IQ
+#undef IR
+#undef MASK