1 . From Java to C++

1. 1. From Java to C++ Yan Shi CS/SE 2630 Lecture Notes

2. C++ Review • if, while, for: • same in Java and C++ • 4 parts of a loop? • EOF loop: [ctrl-z] in Visual Studio • simple C++ data types: • int, long, short, float, double, bool, enum • cin, cout: need to #include<iostream> • Array: intnums[500]; • Reference parameter: for arrays and class objects • String operations: • #include <string> OR • #include <cstring>

3. C++ Class Review • Write the IntList class (IntList0.cpp): • Add, Delete

4. What is different from JAVA? • semicolon at the end of a class declaration • use private: and public: to group data fields and methods • create a IntList object: IntList list; • There are other ways to do that. We will discuss later. • In java: IntList list = new IntList(); • main function: outside the class declaration • use cout instead of System.out.println() • use cin to read from stdin – much easier than Java! • Don’t declare a class as public or private! • How do we declare a public or private class then?

5. Abstract Data Type (ADT) • ADT: a data type whose properties are specified independently of any particular implementation. • Abstraction, Encapsulation, Information hiding • In C++, we use two files for each class: • *.h: header file, class declaration, specification • *.cpp: implementation file, class definition In this way, the class is by default public! If you put everything in one .cpp file without a .h file (like in our previous example), it is a private class.

6. Example Rewrite IntList class into IntList.h and IntList.cpp files • remove implementations from class definition  IntList.h • Note: method documentation belongs in .h file • You can leave on-liner methods in .h file • define methods in IntList.cpp file • What if there are multiple Add functions in the project? • Solution: use scope resolution operator :: • boolIntList::Add( intnewNum){…} • move constintMAX_SIZE;into class IntList: global scope is bad! • have to change to static constintMAX_SIZE; • move the main function into a separate client file IntListClient.cpp • try not to use any I/O in domain classes: that is against the OO design principle! • create a driver/client to utilize domain classes.

7. C++ Preprocessor

8. Lab0.cpp Lab0.obj Lab0.exe SOURCE OBJECT EXECUTABLE written in C++ written in machine language written in machine language via linker via compiler other code from libraries, etc. Running a program • In CS1430, we introduced the compilation process: more details

9. C++ Preprocessor • handle preprocessor directives • macro definitions: #define, #undef • conditional inclusions: #ifdef, #ifndef, #endif, #else and #elif • source file inclusion: #include • remove comments .h files compilation unit(.i) .cpp files

10. Source File Inclusion: #include • Example: • #include <iostream> • #include “IntList.h” • The preprocessor will replace the directive by given file (iostream and IntList.h) • If you have function definitions in the header file, that means they might be copied multiple times if the header file is included in multiple places!  save time at the cost of space! • Difference between <file> and “file”: • #include <file> looks for file in standard directories • #include “file” looks for file in the current directory. That is, file is part of the project! • Never use #include to include a .cppfile in another!

11. Prevent Multiple Inclusion • What if the file is included more than once? • suppose we have Student and StudentList class. In the StudentSystem.cpp file (client), we include both “Student.h” and “StudentList.h”. • Use the inclusion guard! #ifndef _INTLIST_H #define _INTLIST_H regular IntList.h code goes here… #endif • An alternative: #pragma once • less code, avoid name clashes • non-standard, may cause portability issue

12. Macro Definitions #define identifier replacement • When the preprocessor encounters this directive, it replaces any occurrence of identifier in the rest of the code by replacement until #undefis met. • It can be used as a constant definer: #define MAX 9 • This replacement can be an expression, a statement, a block or simply anything. But it should be on the same line. Try to avoid using macros if possible: code that relies heavily on complicated macros may seem obscure to other programmers!

13. Conditional Inclusions • #ifdef, #ifndef, #if, #endif, #else and #elif • These directives allow to include or discard part of the code of a program if a certain condition is met. • Examples: #ifdef SIZE intlist[SIZE]; #endif only compiled if SIZE was previously defined with #define #if SIZE<10 #undef SIZE #define SIZE 10 #elifSIZE>100 #undef SIZE #define SIZE 100 #else #undef SIZE #define SIZE 50 #endif int list[SIZE]; The condition that follows #if or #elif can only evaluate constant expressions, including macro expressions.

14. Stack & Queue Review • Stack is LIFO. • Basic operations: IsEmpty(), IsFull(), Pop(), Push(Item), Top() • Queue is FIFO. • Basic operations: IsEmpty(), IsFull(), Enqueue(Item), Dequeue(Item&) Can we use array to implement them? How?