add numerical recipes library

lib/nr/ansi/examples/xnewt.c

@@ -0,0 +1,36 @@
+
+/* Driver for routine newt */
+
+#include <stdio.h>
+#include <math.h>
+#define NRANSI
+#include "nr.h"
+#include "nrutil.h"
+
+void funcv(int n,float x[],float f[])
+{
+	f[1]=SQR(x[1])+SQR(x[2])-2.0;
+	f[2]=exp(x[1]-1.0)+x[2]*SQR(x[2])-2.0;
+}
+
+#define N 2
+
+int main(void)
+{
+	int i,check;
+	float *x,*f;
+
+	x=vector(1,N);
+	f=vector(1,N);
+	x[1]=2.0;
+	x[2]=0.5;
+	newt(x,N,&check,funcv);
+	funcv(N,x,f);
+	if (check) printf("Convergence problems.\n");
+	printf("%7s %3s %12s\n","Index","x","f");
+	for (i=1;i<=N;i++) printf("%5d %12.6f %12.6f\n",i,x[i],f[i]);
+	free_vector(f,1,N);
+	free_vector(x,1,N);
+	return 0;
+}
+#undef NRANSI