notes/education/software development/ECE1400/Chapter 17 Exercises.md

4. Suppose that the following declarations are in effect:

struct point {int x, y; };
struct rectangle { struct point upper_left, lower_right; };
struct rectangle *p;

Assume that we want p to point to a rectangle structure whose upper left corner is at (10, 25), and whose lower right corner is at (20, 15). Write a series of statements that allocate such a structure and initialize it as indicated.

struct rectangle rect = { { 10, 25 }, { 20, 15 } };
p = ▭

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5. Suppose that f and p are declared as follows:

struct {
	union {
		char a, b;
		int c;
	} d;
	int e[5];
} f, *p = &f;

Which of the following statements are legal?

(a) p->b = ' '; (b) p->e[3] = 10; - Legal (c) (*p).d.a = '*'; - Legal (d) p->d->c = 20;

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7. The following loop is supposed to delete all nodes from a linked list and release the memory that they occupy. Unfortunately, the loop is incorrect. Explain what's wrong with it and show how to fix the bug.

for (p = first; p != NULL; p = p->next)
	free(p);

The above loop won't function because it deallocates the entry, then attempts to access the pointer to the next item, after it's already been freed.

A functional example might look like this:

struct entry* p = first;
while (p != NULL) {
	void *current = p;
	p = p->next;
	free(p);
}

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9. True or false: If x is a structure and a is a member of that structure, then (&x)->a is the same as x.a. Justify your answer.

True: The arrow operator is used to access a member of a struct through a pointer. (&x) creates a pointer to the x struct, therefore the arrow operator can be used to access fields on x.

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13.