monday, mar 31, 2003kate gregory with material from deitel and deitel week 12 labs 4 and 5 are back...

Monday, Mar 31, 2003 Kate Gregorywith material from Deitel and Deitel

Week 12

• Labs 4 and 5 are back

• File IO

• Looking ahead to the final


Date Week Topic ChapterHand Out Due Back Test

6-Jan-03 1Administrivia / Overview / Intro to C++ / Control Structures 1

13-Jan-03 2 Functions / Arrays, Pointers, Strings 2,3,4,5Lab 1 / Lab 2

20-Jan-03 3 Classes, Data Abstraction 6 Lab 1 5%27-Jan-03 4 More on Classes 7 Lab 3 Lab 2 5%3-Feb-03 5 No Lecture

10-Feb-03 6 Operator Overloading 8 Lab 4 Lab 3 5%17-Feb-03 Reading Break24-Feb-03 7 Inheritance 9 Lab 4 5% Midterm 25%3-Mar-03 8 Virtual Functions and Polymorphism 10 Lab 5

10-Mar-03 9 Stream IO 11 Lab 6 Lab 5 5%17-Mar-03 10 Templates 12,13 Lab 7 Lab 6 5%24-Mar-03 11 Exceptions Lab 7 5%31-Mar-03 12 File IO 1417-Apr-03 Exam Final 40%


Lab 4

• Use const every chance you get– The compiler will let you know if it’s wrong– But don’t bother with foo(const int i)

• Reuse, reuse, reuse• Floating point division is expensive and

inaccurate– The point of a Fraction class is to do better than

that


Lab 5

• Protected methods are your best choice when the derived classes really need access to a base class variable

• Use const, use initializer syntax, delegate to the base class

• Choose good test data• Classes with a virtual function need a

virtual destructor


File IO

• Based on the stream IO you already know

• Include <fstream> as well as <iostream>

• The operator << and >> overloads you write will work with files just as with cout and cin


Writing text to a file#include <iostream>#include <fstream>using namespace std;

int main(){ofstream outputfile("out.txt");outputfile << "Hi there" << endl;

return 0;}


Opening and closing• The constructor opens the file• The destructor closes it• You can close it yourself if you need to –

for example to make sure that others can read the file even while your application is still running

• You can use the default constructor, then open it yourself later by calling open()


Reading text from a file

ifstream inputfile("out.txt");

char input [100];

inputfile.getline(input, 100);

cout << "file contains:"

<< endl;

cout << input << endl;


Working with your operatorsEmployee e( -- whatever -- );cout << e;

outputfile << e; // uses your operator

• You might write a different operator for ofstream and format the output differently

• You’re the programmer!


Open modes• The defaults are good for most people, but you

might want to use some of the “open modes”– ios::app– ios::ate (position at end, can move)– ios::in– ios::out– ios::trunc (out and trunc both toss whatever is already

in the file)– ios::binary

• You can combine these with bitwise or |


Opening for append

ofstream outputfile("out.txt",

ios::app);• Everything will be written after what is

already in the file

• Good for logs


Looping through a fileifstream inputfile("out.txt");

char input [100];

cout << "file contains:" << endl;

while (!inputfile.eof())

{

inputfile.getline(input, 100);

cout << input << endl;

}


Class Topics• Control Structures, Functions• Arrays, Pointers, Strings• Classes, Data Abstraction• Operator Overloading• Inheritance• Virtual Functions and Polymorphism• Stream IO• Templates• Exceptions• File IO


There is no next class

• Get ready for the final!– Thursday April 17th, 9am-noon, AC

monday, mar 31, 2003kate gregory with material from deitel and deitel week 12 labs 4 and 5 are back...

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