add numerical recipes library

lib/nr/ansi/examples/xlocate.c

@@ -0,0 +1,41 @@
+
+/* Driver for routine locate */
+
+#include <stdio.h>
+#include <math.h>
+#define NRANSI
+#include "nr.h"
+#include "nrutil.h"
+
+#define N 100
+
+int main(void)
+{
+	unsigned long i,j;
+	float x,*xx;
+
+	xx=vector(1,N);
+	/* create array to be searched */
+	for (i=1;i<=N;i++)
+		xx[i]=exp(i/20.0)-74.0;
+	printf("\nresult of:  j=0 indicates x too small\n");
+	printf("%11s j=100 indicates x too large"," ");
+	printf("\n%10s %6s %11s %12s \n","locate ","j","xx(j)","xx(j+1)");
+	/* perform test */
+	for (i=1;i<=19;i++) {
+		x = -100.0+200.0*i/20.0;
+		locate(xx,N,x,&j);
+		if ((j < N) && (j > 0))
+			printf("%10.4f %6lu %12.6f %12.6f\n",
+				x,j,xx[j],xx[j+1]);
+		else if (j == N)
+			printf("%10.4f %6lu %12.6f %s\n",
+				x,j,xx[j],"   upper lim");
+		else
+			printf("%10.4f %6lu %s %12.6f \n",
+				x,j,"   lower lim",xx[j+1]);
+	}
+	free_vector(xx,1,N);
+	return 0;
+}
+#undef NRANSI