CS 330 Lecture 24 – Memory, Polymorphism, and Higher-order Functions
Agenda
- what ?s
- program this
- polymorphism in C
- function pointers
- callbacks with GLUT
TODO
- 1/4 sheet: read A Malloc Tutorial.
Program This
- Write a preprocessor macro named
EZMALLOCthat shortens the code needed to allocate a block of memory. Programmers will invoke it with something like:int *numbers = EZMALLOC(...);
Code
multireturn.c
#include <stdio.h>
#include <stdlib.h>
/* [int, int] divmod(int numerator, int denominator) { */
/* return [numerator / denominator, numerator % denominator]; */
/* } */
void divmod(int numerator, int denominator, int *quotient, int *remainder) {
*quotient = numerator / denominator;
*remainder = numerator % denominator;
}
int main(int argc, char **argv) {
int quotient, remainder;
divmod(500, 9, "ient, &remainder);
printf("quotient: %d\n", quotient);
printf("remainder: %d\n", remainder);
return 0;
}
poly.c
#include <stdio.h>
#include <stdlib.h>
int find_minear(void *list,
int nbytes_per_element,
int nelements,
int (*compare)(void *a, void *b)) {
// assume first is min
// for each remaining element
// try to oust min with element i
//
// return i
int imin = 0;
for (int i = 1; i < nelements; ++i) {
void *min_so_far = list + imin * nbytes_per_element;
void *usurper = list + i * nbytes_per_element;
if (compare(min_so_far, usurper) > 0) {
imin = i;
}
}
return imin;
}
int int_compare(void *a, void *b) {
int *ai = (int *) a;
int *bi = (int *) b;
if (*ai < *bi) {
return -1;
} else if (*ai == *bi) {
return 0;
} else {
return 1;
}
}
int main(int argc, char **argv) {
int numbers[] = {
9, 7, 99, 42, 12, 3, 500, 999
};
int imin = find_minear(numbers, sizeof(int), 8, int_compare);
printf("numbers[imin]: %d\n", numbers[imin]);
return 0;
}
torus.c
#include <stdio.h>
#include <stdlib.h>
#include <GLUT/glut.h>
int x_angle = 0;
int y_angle = 0;
void on_draw() {
glClear(GL_COLOR_BUFFER_BIT);
glLoadIdentity();
glRotatef(x_angle, 1.0f, 0.0f, 0.0f);
glRotatef(y_angle, 0.0f, 1.0f, 0.0f);
glutWireTorus(0.3f, 0.5f, 10, 10);
glutSwapBuffers();
}
void on_key(unsigned char key, int mouse_x, int mouse_y) {
switch (key) {
case 'x':
++x_angle;
break;
case 'X':
--x_angle;
break;
case 'y':
++y_angle;
break;
case 'Y':
--y_angle;
break;
}
glutPostRedisplay();
}
int main(int argc, char **argv) {
glutInit(&argc, argv);
glutCreateWindow("My first torus");
glutDisplayFunc(on_draw);
glutKeyboardFunc(on_key);
glutMainLoop();
printf("sdafasd\n");
return 0;
}
Haiku
an algorithm with holes:
To live a _____ life
Drink 8 _____ everyday
Marry your first _____
To live a _____ life
Drink 8 _____ everyday
Marry your first _____