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

> **4.** Suppose that the following declarations are in effect:
```c
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.

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

---

> **5.** Suppose that `f` and `p` are declared as follows:
```c
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;`

---

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

---

> **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`.

---

> **13.**