exercise07.c

// C Primer Plus
// Chapter 16 Exercise 7:

// Here’s a partial program using a variadic function:

// 	#include <stdio.h>
// 	#include <stdlib.h>
// 	#include <stdarg.h>

// 	void show_array(const double ar[], int n);
// 	double * new_d_array(int n, ...);

// 	int main() {
// 		double * p1;
// 		double * p2;
// 		p1 = new_d_array(5, 1.2, 2.3, 3.4, 4.5, 5.6);
// 		p2 = new_d_array(4, 100.0, 20.00, 8.08, -1890.0);
//		show_array(p1, 5);
// 		show_array(p2, 4);
// 		free(p1);
// 		free(p2);
// 		return 0;
// 	}

// The new_d_array() function takes an int argument and a variable number of
// double arguments. The function returns a pointer to a block of memory
// allocated by malloc(). The int argument indicates the number of elements to
// be in the dynamic array, and the double values are used to initialize the
// elements, with the first value being assigned to the first element, and so
// on. Complete the program by providing the code for show_ array() and
// new_d_array().

#include <stdio.h>
#include <stdlib.h>
#include <stdarg.h>

void show_array(const double ar[], int n);
double * new_d_array(int n, ...);

int main()
{
	double * p1;
	double * p2;
	p1 = new_d_array(5, 1.2, 2.3, 3.4, 4.5, 5.6);
	p2 = new_d_array(4, 100.0, 20.00, 8.08, -1890.0); 
	show_array(p1, 5);
	show_array(p2, 4);
	free(p1);
	free(p2);
	return 0;
}

void show_array(const double ar[], int n)
{
	printf("{");
	for (int i = 0; i < n; i++)
	{
		printf("%.3f", ar[i]);
		if (i < n - 1)
			printf(", ");
		if (i % 20 == 19)
			printf("\n");
	}
	puts("}");
}

double * new_d_array(int n, ...)
{
	va_list ap;
	va_start(ap, n);

	double * arr = (double *) malloc(n * sizeof(double));
	if (!arr)
		fprintf(stderr, "Could not allocate memory.\n");
	else
		for (int i = 0; i < n; i++)
			arr[i] = va_arg(ap, double);

	return arr;
}