add numerical recipes library

lib/nr/ansi/examples/xvoltra.c

@@ -0,0 +1,43 @@
+
+/* Driver for routine voltra */
+#include <stdio.h>
+#include <math.h>
+#define NRANSI
+#include "nr.h"
+#include "nrutil.h"
+
+float g(int k,float t)
+{
+	return (k == 1 ? cosh(t)+t*sin(t) : 2.0*sin(t)+t*(SQR(sin(t))+exp(t)));
+}
+
+float ak(int k,int l,float t,float s)
+{
+	return ((k == 1) ?
+		(l == 1 ? -exp(t-s) : -cos(t-s)) :
+		(l == 1 ? -exp(t+s) : -t*cos(s)));
+}
+
+#define N 30
+#define H 0.05
+#define M 2
+
+int main(void)
+{
+	int nn;
+	float t0=0.0,*t,**f;
+
+	t=vector(1,N);
+	f=matrix(1,M,1,N);
+	voltra(N,M,t0,H,t,f,g,ak);
+	/* exact soln is f[1]=exp(-t), f[2]=2sin(t) */
+	printf("  abscissa, voltra answer1, real answer1,");
+	printf(" voltra answer2, real answer2\n");
+	for (nn=1;nn<=N;nn++)
+		printf("%12.6f %12.6f %12.6f %12.6f %12.6f\n",
+			t[nn],f[1][nn],exp(-t[nn]),f[2][nn],2.0*sin(t[nn]));
+	free_vector(t,1,N);
+	free_matrix(f,1,M,1,N);
+	return 0;
+}
+#undef NRANSI