add numerical recipes library

lib/nr/ansi/examples/xgasdev.c

@@ -0,0 +1,41 @@
+
+/* Driver for routine gasdev */
+
+#include <stdio.h>
+#define NRANSI
+#include "nr.h"
+
+#define N 20
+#define NOVER2 (N/2)
+#define NPTS 10000
+#define ISCAL 400
+#define LLEN 50
+
+int main(void)
+{
+	char words[LLEN+1];
+	int i,j,k,klim,dist[N+1];
+	long idum=(-13);
+	float dd,x;
+
+	for (j=0;j<=N;j++) dist[j]=0;
+	for (i=1;i<=NPTS;i++) {
+		x=0.25*N*gasdev(&idum);
+		j=(int)(x > 0 ? x+0.5 : x-0.5);
+		if ((j >= -NOVER2) && (j <= NOVER2)) ++dist[j+NOVER2];
+	}
+	printf("Normally distributed deviate of %6d points\n",NPTS);
+	printf ("%5s %10s %9s\n","x","p(x)","graph:");
+	for (j=0;j<=N;j++) {
+		dd=(float) dist[j]/NPTS;
+		for (k=1;k<=LLEN;k++) words[k]=' ';
+		klim=(int) (ISCAL*dd);
+		if (klim > LLEN)  klim=LLEN;
+		for (k=1;k<=klim;k++) words[k]='*';
+		printf("%8.4f %8.4f  ",j/(0.25*N),dd);
+		for (k=1;k<=LLEN;k++) printf("%c",words[k]);
+		printf("\n");
+	}
+	return 0;
+}
+#undef NRANSI