xlocate.c

Numerical Recipes in C的源代码

/* 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