notes/education/computer engineering/ECE1400/Chapter 9 Exercises.md

1. The following function, which computes the area of a triangle, contains two errors. Locate the errors and show how to fix them. (Hint: There are no errors in the formula)

double triangle_area(double base, height)
double product;
{
	product = base * height;
	return product / 2;
}

Answer:

// A type annotation is needed for `height`
double triangle_area(double base, double height)
{
	// The `product` variable declaration was not in the function block.
	double product;
	product = base * height;
	return product / 2;
}

2. Write a function check(x, y, n) that returns 1 if both x and y fall between zero and n - 1 inclusive. The function should return 0 otherwise. Assume that x, y, and n are all of type int

int check(int x, int y, int n) {
	int in_range = 1;
	if (x < 0 || y < 0) {
		in_range = 0;
	}
	if (x > n - 1 || y > n - 1) {
		in_range = 0;
	}

	return in_range;
}

7. Suppose that function f has the following definition: int f(int a, int b) { ... } Which of the following statements are legal? Assume that i has type int and x has type double).

Answer: All of them are legal and will compile and run. (c) and (d) are what I would consider bad practice because they perform an implicit conversion from a double to an int, and should include an explicit cast.

8. Which of the following would be valid prototypes for a function that returns nothing and has one double parameter?

Answer: (a) and (b). Parameters must contain a type annotation but they do not need to specify a name. A function prototype declaration must specify a return type.

9. What will be the output of the following program?

#include <stdio.h>

void swap (int a, int b);

int main(void)
{
    int i = 1, j = 2;
    swap(i, j);
    printf("i = %d, j = %d\n", i, j);
    return 0;
}

void swap(int a, int b)
{
    int temp = a;
    a = b;
    b = temp;
}

Answer:

i = 1, j = 2

Because function parameters are passed by value and not reference in C, modifications to a and b are limited to the scope of swap.