Program Driver file for trapezd.c routine

/* This is a C program to integrate f(x) in the interval a<= x <= b  
*  using the composite trapezoidal method described in class. */
/* Illustrates the use of NRC */ 
/* See page 293 of ABC for passing functions as arguements */ 
 
#include <stdio.h>
#include <math.h>
#include "nr.h"
#include "nrutil.h"
 
float func(float); 
float trapzd( float (*func)(float), float low_lim, float up_lim, int ntr); 
int main(void)
{
        float integral,low_lim,up_lim;
        int i,ntr;
/* 
* Read the lower and upper limits of the integral, and the number of 
* trapezoids to be used = ntr
*/ 
        printf("Enter the lower and upper bounds:\n");
        scanf("%f%f",&low_lim,&up_lim);
        printf("Value of n(>0): number of trapezoids used is 2^n+1.\n");
        scanf("%d",&ntr);
/* */ 
        for(i=1; i<=ntr+1; i++)  integral = trapzd(func,low_lim,up_lim,i); 
/* */
        printf("Integral is %e\n",integral); 
} 
float func(float x)
{
        float pi;
        pi = 4.0*atan(1.0); 
        return exp(-x*x/2.0)/sqrt(2.0*pi);      
}