add numerical recipes library

lib/nr/ansi/examples/xbeschb.c

@@ -0,0 +1,29 @@
+
+/* Driver for routine beschb */
+
+#include <stdio.h>
+#include <math.h>
+#define NRANSI
+#include "nr.h"
+#include "nrutil.h"
+
+int main(void)
+{
+	double gam1,gam2,gampl,gammi,x,xgam1,xgam2,xgampl,xgammi;
+
+	for (;;) {
+		printf("Enter x:\n");
+		if (scanf("%lf",&x) == EOF) break;
+		beschb(x,&xgam1,&xgam2,&xgampl,&xgammi);
+		printf("%5s\n%17s %16s %17s %15s\n%17s %16s %17s %15s\n",
+			"x","gam1","gam2","gampl","gammi","xgam1","xgam2","xgampl","xgammi");
+		gampl=1/exp(gammln((float)(1+x)));
+		gammi=1/exp(gammln((float)(1-x)));
+		gam1=(gammi-gampl)/(2*x);
+		gam2=(gammi+gampl)/2;
+		printf("%5.2f\n\t%16.6e %16.6e %16.6e %16.6e\n",x,gam1,gam2,gampl,gammi);
+		printf("\t%16.6e %16.6e %16.6e %16.6e\n",xgam1,xgam2,xgampl,xgammi);
+	}
+	return 0;
+}
+#undef NRANSI