1. Homework Finishing K&R Chapter 5 today Starting K&R Chapter 6 next
Skipping sections for now
Not covering section 5.12
Starting K&R Chapter 6 next

2. Pointers to Functions, K&R 5.11
Function prototype with pointer to function
void qsort ( … , int (*comp) (void *, void *));
Function call passing a pointer to function
qsort( … , (int (*) (void *, void *)) strcmp);
This is a cast to function pointer of strcmp
Within qsort(), function is called via a pointer
if ((*comp) (v[i], v[left]) < 0) …
Address of a function
Qsort will use comp function. Different sorting functions

3. Pointers to Functions Initialize a pointer to a function
/* function pointer *fooptr = cast of foo to func ptr */
int (*fooptr) (int *, int*) = (int (*) (int *, int *)) foo;
Call the function foo via the pointer to it
(*fooptr) (to, from);
This allows you to pass a function name dynamically to another function. We don’t do much with this concept in this course.
END OF POINTERS

4. structs, K&R 6
A struct is a collection of variables, possibly of different types, grouped under a single name for common reference as a unit.
struct point { /* with optional tag */
int x; /* member x */
int y; /* member y */
} pt, q; /* variable names */
or struct { /* w/o optional tag */
int x, y; /* two members */
} pt, q; /* variable names */
Size of them

5. structs The defined struct point is like a new “type”
With the tag, point, can declare other variables:
struct point pt1, maxpt = {320, 200};
Reference to struct members:
pt1.x = 320; pt1.y = 200; /* alternate init */
printf("(%d, %d)\n", pt1.x, pt1.y);
/* prints out as (320, 200) */
Struct.element

6. structs Defining a struct inside a struct (nesting). struct rect {
struct point pt1; /* lower left */
struct point pt2; /* upper right */ };
struct rect box;/* declare box as a rect */
You can First define it then use it

7. structs pt1 is lower left hand corner of box
pt2 is upper right hand corner of box:
box.pt1.x < box.pt2.x box.pt1.y < box.pt2.y y
box.pt2.y
To get area
box.pt1.y x
box.pt1.x
box.pt2.x

8. structs /* Find area of a rectangle */ int area = rectarea (box); …
int rectarea (struct rect x) {
return (x.pt2.x - x.pt1.x) * (x.pt2.y - x.pt1.y); }

9. structs Memory allocation for structs Two point structs pt1 and pt2
One rect struct box containing two point structs
pt1
pt2
pt1.x
pt1.y
pt2.x
pt2.y
box
pt1
pt2
pt1.x
pt1.y
pt2.x
pt2.y