troll batul How might you model a battle between two trolls? How - PowerPoint PPT Presentation

CSCI261 Lecture 23: Passing by Reference, Objects and Memory troll batul

How might you model a battle between two trolls?

How might you model a battle between two trolls? Define and describe trolls (attributes, behavior) Describe the battle process (to the death!) Define who wins (who is left standing)

Declaring functions in external files

Header & Implementation Files volume.h #include <cstdlib> #include <iostream> #pragma once #include <string> #include “volume.h” int volume(int h, int w, int d); using namespace std; int main() { // ... cout << "The volume is " << volume(20, 30, 40); volume.cpp return 0; #include “volume.h” } int volume(int h, int w, int d) { return h * w * d; }

Header & Implementation Files Header file (.h) contains the function prototypes. Implementation file (.cpp) contains the definitions.

Header & Implementation FIles ship.h object files int speed(int thrust); (compile) coolgame.exe ship.cpp int speed(int thrust) { (link) 1010 return thrust * 10; 0010 } 0010 1010 main.cpp (compile) #include “ships.h” 0 main int main() { // cool stuff }

Passing arguments by reference

What? Why? Arguments are passed by value... int free_beer(int beers); f()’s beers main()’s beers int main() { 10 int beers(10); cout << beers; a copy is made 10 10 cout << free_beer(beers); cout << beers; // ... passed to f() 10 } 10 f()’s beers is 10 int free_beer(int beers) { cout << beers; 0 beers = 0; cout << beers; 0 return beers; }

...or by reference Your new friend: & f()’s beers main()’s beers int free_beer(int& beers); int main() { 10 int beers(10); cout << beers; 10 cout << free_beer(beers); // ... } 10 int free_beer(int& beers) { cout << beers; 0 beers = 0; cout << beers; return beers; 0 }

void makeZero(int n) { void makeZero(int &n) { n = 0; n = 0; } } x x 3 3 makeZero(x); makeZero(x); the value of x is “copied” and passed to makeZero as n a reference to x itself is passed to makeZero as n makeZero makeZero n n 3 3 n n 0 0 x x 3 0

Troll fred(“Fur-red”); MEMORY fred name => “Fur-red” height => 20 weight =>376 fred

What? Huh? In general, always pass objects by reference.

Homework • Read Etter 5.3 troll batul • Complete 29_trollBattle