add numerical recipes library

lib/nr/ansi/examples/xfred2.c

@@ -0,0 +1,41 @@
+
+/* Driver for routine fred2 */
+
+#include <stdio.h>
+#include <math.h>
+#define NRANSI
+#include "nr.h"
+#include "nrutil.h"
+
+#define N 8
+#define PI 3.1415927
+
+float g(float t)
+{
+	return sqrt(t)-pow(PI/2.0,2.25)*pow(t,0.75)/2.25;
+}
+
+float ak(float t,float s)
+{
+	return pow(t*s,0.75);
+}
+
+int main(void)
+{
+	int i;
+	float a=0.0,b=PI/2.0,*f;
+	float *t,*w;
+
+	t=vector(1,N);
+	f=vector(1,N);
+	w=vector(1,N);
+	fred2(N,a,b,t,f,w,g,ak);
+	/* Compare with exact solution */
+	printf("Abscissa, Calc soln, True soln\n");
+	for (i=1;i<=N;i++) printf("%10.6f %10.6f %10.6f\n",t[i],f[i],sqrt(t[i]));
+	free_vector(w,1,N);
+	free_vector(f,1,N);
+	free_vector(t,1,N);
+	return 0;
+}
+#undef NRANSI