add numerical recipes library

lib/nr/ansi/examples/xtrapzd.c

@@ -0,0 +1,38 @@
+
+/* Driver for routine trapzd */
+
+#include <stdio.h>
+#include <math.h>
+#define NRANSI
+#include "nr.h"
+
+#define NMAX 14
+#define PIO2 1.5707963
+
+/* Test function */
+float func(float x)
+{
+	return (x*x)*(x*x-2.0)*sin(x);
+}
+
+/* Integral of test function */
+float fint(float x)
+{
+	return 4.0*x*(x*x-7.0)*sin(x)-(pow(x,4.0)-14.0*(x*x)+28.0)*cos(x);
+}
+
+int main(void)
+{
+	int i;
+	float a=0.0,b=PIO2,s;
+
+	printf("\nIntegral of func with 2^(n-1) points\n");
+	printf("Actual value of integral is %10.6f\n",fint(b)-fint(a));
+	printf("%6s %24s\n","n","approx. integral");
+	for (i=1;i<=NMAX;i++) {
+		s=trapzd(func,a,b,i);
+		printf("%6d %20.6f\n",i,s);
+	}
+	return 0;
+}
+#undef NRANSI