- •Contents
- •Introduction
- •Who This Book Is For
- •What This Book Covers
- •How This Book Is Structured
- •What You Need to Use This Book
- •Conventions
- •Source Code
- •Errata
- •p2p.wrox.com
- •The Basics of C++
- •The Obligatory Hello, World
- •Namespaces
- •Variables
- •Operators
- •Types
- •Conditionals
- •Loops
- •Arrays
- •Functions
- •Those Are the Basics
- •Diving Deeper into C++
- •Pointers and Dynamic Memory
- •Strings in C++
- •References
- •Exceptions
- •The Many Uses of const
- •C++ as an Object-Oriented Language
- •Declaring a Class
- •Your First Useful C++ Program
- •An Employee Records System
- •The Employee Class
- •The Database Class
- •The User Interface
- •Evaluating the Program
- •What Is Programming Design?
- •The Importance of Programming Design
- •Two Rules for C++ Design
- •Abstraction
- •Reuse
- •Designing a Chess Program
- •Requirements
- •Design Steps
- •An Object-Oriented View of the World
- •Am I Thinking Procedurally?
- •The Object-Oriented Philosophy
- •Living in a World of Objects
- •Object Relationships
- •Abstraction
- •Reusing Code
- •A Note on Terminology
- •Deciding Whether or Not to Reuse Code
- •Strategies for Reusing Code
- •Bundling Third-Party Applications
- •Open-Source Libraries
- •The C++ Standard Library
- •Designing with Patterns and Techniques
- •Design Techniques
- •Design Patterns
- •The Reuse Philosophy
- •How to Design Reusable Code
- •Use Abstraction
- •Structure Your Code for Optimal Reuse
- •Design Usable Interfaces
- •Reconciling Generality and Ease of Use
- •The Need for Process
- •Software Life-Cycle Models
- •The Stagewise and Waterfall Models
- •The Spiral Method
- •The Rational Unified Process
- •Software-Engineering Methodologies
- •Extreme Programming (XP)
- •Software Triage
- •Be Open to New Ideas
- •Bring New Ideas to the Table
- •Thinking Ahead
- •Keeping It Clear
- •Elements of Good Style
- •Documenting Your Code
- •Reasons to Write Comments
- •Commenting Styles
- •Comments in This Book
- •Decomposition
- •Decomposition through Refactoring
- •Decomposition by Design
- •Decomposition in This Book
- •Naming
- •Choosing a Good Name
- •Naming Conventions
- •Using Language Features with Style
- •Use Constants
- •Take Advantage of const Variables
- •Use References Instead of Pointers
- •Use Custom Exceptions
- •Formatting
- •The Curly Brace Alignment Debate
- •Coming to Blows over Spaces and Parentheses
- •Spaces and Tabs
- •Stylistic Challenges
- •Introducing the Spreadsheet Example
- •Writing Classes
- •Class Definitions
- •Defining Methods
- •Using Objects
- •Object Life Cycles
- •Object Creation
- •Object Destruction
- •Assigning to Objects
- •Distinguishing Copying from Assignment
- •The Spreadsheet Class
- •Freeing Memory with Destructors
- •Handling Copying and Assignment
- •Different Kinds of Data Members
- •Static Data Members
- •Const Data Members
- •Reference Data Members
- •Const Reference Data Members
- •More about Methods
- •Static Methods
- •Const Methods
- •Method Overloading
- •Default Parameters
- •Inline Methods
- •Nested Classes
- •Friends
- •Operator Overloading
- •Implementing Addition
- •Overloading Arithmetic Operators
- •Overloading Comparison Operators
- •Building Types with Operator Overloading
- •Pointers to Methods and Members
- •Building Abstract Classes
- •Using Interface and Implementation Classes
- •Building Classes with Inheritance
- •Extending Classes
- •Overriding Methods
- •Inheritance for Reuse
- •The WeatherPrediction Class
- •Adding Functionality in a Subclass
- •Replacing Functionality in a Subclass
- •Respect Your Parents
- •Parent Constructors
- •Parent Destructors
- •Referring to Parent Data
- •Casting Up and Down
- •Inheritance for Polymorphism
- •Return of the Spreadsheet
- •Designing the Polymorphic Spreadsheet Cell
- •The Spreadsheet Cell Base Class
- •The Individual Subclasses
- •Leveraging Polymorphism
- •Future Considerations
- •Multiple Inheritance
- •Inheriting from Multiple Classes
- •Naming Collisions and Ambiguous Base Classes
- •Interesting and Obscure Inheritance Issues
- •Special Cases in Overriding Methods
- •Copy Constructors and the Equals Operator
- •The Truth about Virtual
- •Runtime Type Facilities
- •Non-Public Inheritance
- •Virtual Base Classes
- •Class Templates
- •Writing a Class Template
- •How the Compiler Processes Templates
- •Distributing Template Code between Files
- •Template Parameters
- •Method Templates
- •Template Class Specialization
- •Subclassing Template Classes
- •Inheritance versus Specialization
- •Function Templates
- •Function Template Specialization
- •Function Template Overloading
- •Friend Function Templates of Class Templates
- •Advanced Templates
- •More about Template Parameters
- •Template Class Partial Specialization
- •Emulating Function Partial Specialization with Overloading
- •Template Recursion
- •References
- •Reference Variables
- •Reference Data Members
- •Reference Parameters
- •Reference Return Values
- •Deciding between References and Pointers
- •Keyword Confusion
- •The const Keyword
- •The static Keyword
- •Order of Initialization of Nonlocal Variables
- •Types and Casts
- •typedefs
- •Casts
- •Scope Resolution
- •Header Files
- •C Utilities
- •Variable-Length Argument Lists
- •Preprocessor Macros
- •How to Picture Memory
- •Allocation and Deallocation
- •Arrays
- •Working with Pointers
- •Array-Pointer Duality
- •Arrays Are Pointers!
- •Not All Pointers Are Arrays!
- •Dynamic Strings
- •C-Style Strings
- •String Literals
- •The C++ string Class
- •Pointer Arithmetic
- •Custom Memory Management
- •Garbage Collection
- •Object Pools
- •Function Pointers
- •Underallocating Strings
- •Memory Leaks
- •Double-Deleting and Invalid Pointers
- •Accessing Out-of-Bounds Memory
- •Using Streams
- •What Is a Stream, Anyway?
- •Stream Sources and Destinations
- •Output with Streams
- •Input with Streams
- •Input and Output with Objects
- •String Streams
- •File Streams
- •Jumping around with seek() and tell()
- •Linking Streams Together
- •Bidirectional I/O
- •Internationalization
- •Wide Characters
- •Non-Western Character Sets
- •Locales and Facets
- •Errors and Exceptions
- •What Are Exceptions, Anyway?
- •Why Exceptions in C++ Are a Good Thing
- •Why Exceptions in C++ Are a Bad Thing
- •Our Recommendation
- •Exception Mechanics
- •Throwing and Catching Exceptions
- •Exception Types
- •Throwing and Catching Multiple Exceptions
- •Uncaught Exceptions
- •Throw Lists
- •Exceptions and Polymorphism
- •The Standard Exception Hierarchy
- •Catching Exceptions in a Class Hierarchy
- •Writing Your Own Exception Classes
- •Stack Unwinding and Cleanup
- •Catch, Cleanup, and Rethrow
- •Use Smart Pointers
- •Common Error-Handling Issues
- •Memory Allocation Errors
- •Errors in Constructors
- •Errors in Destructors
- •Putting It All Together
- •Why Overload Operators?
- •Limitations to Operator Overloading
- •Choices in Operator Overloading
- •Summary of Overloadable Operators
- •Overloading the Arithmetic Operators
- •Overloading Unary Minus and Unary Plus
- •Overloading Increment and Decrement
- •Overloading the Subscripting Operator
- •Providing Read-Only Access with operator[]
- •Non-Integral Array Indices
- •Overloading the Function Call Operator
- •Overloading the Dereferencing Operators
- •Implementing operator*
- •Implementing operator->
- •What in the World Is operator->* ?
- •Writing Conversion Operators
- •Ambiguity Problems with Conversion Operators
- •Conversions for Boolean Expressions
- •How new and delete Really Work
- •Overloading operator new and operator delete
- •Overloading operator new and operator delete with Extra Parameters
- •Two Approaches to Efficiency
- •Two Kinds of Programs
- •Is C++ an Inefficient Language?
- •Language-Level Efficiency
- •Handle Objects Efficiently
- •Use Inline Methods and Functions
- •Design-Level Efficiency
- •Cache as Much as Possible
- •Use Object Pools
- •Use Thread Pools
- •Profiling
- •Profiling Example with gprof
- •Cross-Platform Development
- •Architecture Issues
- •Implementation Issues
- •Platform-Specific Features
- •Cross-Language Development
- •Mixing C and C++
- •Shifting Paradigms
- •Linking with C Code
- •Mixing Java and C++ with JNI
- •Mixing C++ with Perl and Shell Scripts
- •Mixing C++ with Assembly Code
- •Quality Control
- •Whose Responsibility Is Testing?
- •The Life Cycle of a Bug
- •Bug-Tracking Tools
- •Unit Testing
- •Approaches to Unit Testing
- •The Unit Testing Process
- •Unit Testing in Action
- •Higher-Level Testing
- •Integration Tests
- •System Tests
- •Regression Tests
- •Tips for Successful Testing
- •The Fundamental Law of Debugging
- •Bug Taxonomies
- •Avoiding Bugs
- •Planning for Bugs
- •Error Logging
- •Debug Traces
- •Asserts
- •Debugging Techniques
- •Reproducing Bugs
- •Debugging Reproducible Bugs
- •Debugging Nonreproducible Bugs
- •Debugging Memory Problems
- •Debugging Multithreaded Programs
- •Debugging Example: Article Citations
- •Lessons from the ArticleCitations Example
- •Requirements on Elements
- •Exceptions and Error Checking
- •Iterators
- •Sequential Containers
- •Vector
- •The vector<bool> Specialization
- •deque
- •list
- •Container Adapters
- •queue
- •priority_queue
- •stack
- •Associative Containers
- •The pair Utility Class
- •multimap
- •multiset
- •Other Containers
- •Arrays as STL Containers
- •Strings as STL Containers
- •Streams as STL Containers
- •bitset
- •The find() and find_if() Algorithms
- •The accumulate() Algorithms
- •Function Objects
- •Arithmetic Function Objects
- •Comparison Function Objects
- •Logical Function Objects
- •Function Object Adapters
- •Writing Your Own Function Objects
- •Algorithm Details
- •Utility Algorithms
- •Nonmodifying Algorithms
- •Modifying Algorithms
- •Sorting Algorithms
- •Set Algorithms
- •The Voter Registration Audit Problem Statement
- •The auditVoterRolls() Function
- •The getDuplicates() Function
- •The RemoveNames Functor
- •The NameInList Functor
- •Testing the auditVoterRolls() Function
- •Allocators
- •Iterator Adapters
- •Reverse Iterators
- •Stream Iterators
- •Insert Iterators
- •Extending the STL
- •Why Extend the STL?
- •Writing an STL Algorithm
- •Writing an STL Container
- •The Appeal of Distributed Computing
- •Distribution for Scalability
- •Distribution for Reliability
- •Distribution for Centrality
- •Distributed Content
- •Distributed versus Networked
- •Distributed Objects
- •Serialization and Marshalling
- •Remote Procedure Calls
- •CORBA
- •Interface Definition Language
- •Implementing the Class
- •Using the Objects
- •A Crash Course in XML
- •XML as a Distributed Object Technology
- •Generating and Parsing XML in C++
- •XML Validation
- •Building a Distributed Object with XML
- •SOAP (Simple Object Access Protocol)
- •. . . Write a Class
- •. . . Subclass an Existing Class
- •. . . Throw and Catch Exceptions
- •. . . Read from a File
- •. . . Write to a File
- •. . . Write a Template Class
- •There Must Be a Better Way
- •Smart Pointers with Reference Counting
- •Double Dispatch
- •Mix-In Classes
- •Object-Oriented Frameworks
- •Working with Frameworks
- •The Model-View-Controller Paradigm
- •The Singleton Pattern
- •Example: A Logging Mechanism
- •Implementation of a Singleton
- •Using a Singleton
- •Example: A Car Factory Simulation
- •Implementation of a Factory
- •Using a Factory
- •Other Uses of Factories
- •The Proxy Pattern
- •Example: Hiding Network Connectivity Issues
- •Implementation of a Proxy
- •Using a Proxy
- •The Adapter Pattern
- •Example: Adapting an XML Library
- •Implementation of an Adapter
- •Using an Adapter
- •The Decorator Pattern
- •Example: Defining Styles in Web Pages
- •Implementation of a Decorator
- •Using a Decorator
- •The Chain of Responsibility Pattern
- •Example: Event Handling
- •Implementation of a Chain of Responsibility
- •Using a Chain of Responsibility
- •Example: Event Handling
- •Implementation of an Observer
- •Using an Observer
- •Chapter 1: A Crash Course in C++
- •Chapter 3: Designing with Objects
- •Chapter 4: Designing with Libraries and Patterns
- •Chapter 5: Designing for Reuse
- •Chapter 7: Coding with Style
- •Chapters 8 and 9: Classes and Objects
- •Chapter 11: Writing Generic Code with Templates
- •Chapter 14: Demystifying C++ I/O
- •Chapter 15: Handling Errors
- •Chapter 16: Overloading C++ Operators
- •Chapter 17: Writing Efficient C++
- •Chapter 19: Becoming Adept at Testing
- •Chapter 20: Conquering Debugging
- •Chapter 24: Exploring Distributed Objects
- •Chapter 26: Applying Design Patterns
- •Beginning C++
- •General C++
- •I/O Streams
- •The C++ Standard Library
- •C++ Templates
- •Integrating C++ and Other Languages
- •Algorithms and Data Structures
- •Open-Source Software
- •Software-Engineering Methodology
- •Programming Style
- •Computer Architecture
- •Efficiency
- •Testing
- •Debugging
- •Distributed Objects
- •CORBA
- •XML and SOAP
- •Design Patterns
- •Index
Chapter 1
Breaking up the statement into separate lines makes it even clearer:
int i = 8 * 2; int j = 21 / 7; j %= 2;
i = 34 + i + j;
For those of you playing along at home, all three approaches are equivalent and end up with i equal to 51. If you assumed that C++ evaluated expressions from left to right, your answer would have been 1. In fact, C++ evaluates /, *, and % first (in left to right order), followed by addition and subtraction, then bitwise operators. Parenthesis let you explicitly tell the compiler that a certain operation should be evaluated separately.
Types
In C++, you can use the basic types (int, bool, etc.) to build more complex types of your own design. Once you are an experienced C++ programmer, you will rarely use the following techniques, which are features brought in from C, because classes are far more powerful. Still, it is important to know about the two most common ways of building types so that you will recognize the syntax.
Enumerated Types
An integer really represents a value within a sequence — the sequence of numbers. Enumerated types let you define your own sequences so that you can declare variables with values in that sequence. For example, in a chess program, you could represent each piece as an int, with constants for the piece types, as shown in the following code. The integers representing the types are marked const to indicate that they can never change.
const int kPieceTypeKing = 0; const int kPieceTypeQueen = 1; const int kPieceTypeRook = 2; const int kPieceTypePawn = 3; //etc.
int myPiece = kPieceTypeKing;
This representation is fine, but it can become dangerous. Since the piece is just an int, what would happen if another programmer added code to increment the value of the piece? By adding one, a king becomes a queen, which really makes no sense. Worse still, someone could come in and give a piece a value of -1, which has no corresponding constant.
Enumerated types resolve these problems by tightly defining the range of values for a variable. The following code declares a new type, PieceT, that has four possible values, representing four of the chess pieces.
typedef enum { kPieceTypeKing, kPieceTypeQueen, kPieceTypeRook, kPieceTypePawn
} PieceT;
10
A Crash Course in C++
Behind the scenes, an enumerated type is just an integer value. The real value of kPieceTypeKing is zero. However, by defining the possible values for variables of type PieceT, your compiler can give you a warning or error if you attempt to perform arithmetic on PieceT variables or treat them as integers. The following code, which declares a PieceT variable then attempts to use it as an integer, results in a warning on most compilers.
PieceT myPiece;
myPiece = 0;
Structs
Structs let you encapsulate one or more existing types into a new type. The classic example of a struct is a database record. If you are building a personnel system to keep track of employee information, you will need to store the first initial, last initial, middle initial, employee number, and salary for each employee. A struct that contains all of this information is shown in the header file that follows.
// employeestruct.h
typedef struct {
char |
firstInitial; |
char |
middleInitial; |
char |
lastInitial; |
int |
employeeNumber; |
int |
salary; |
} EmployeeT; |
|
A variable declared with type EmployeeT will have all of these fields built-in. The individual fields of a struct can be accessed by using the “.” character. The example that follows creates and then outputs the record for an employee.
// structtest.cpp
#include <iostream> #include “employeestruct.h”
using namespace std;
int main(int argc, char** argv)
{
// Create and populate an employee. EmployeeT anEmployee;
anEmployee.firstInitial = ‘M’; anEmployee.middleInitial = ‘R’; anEmployee.lastInitial = ‘G’; anEmployee.employeeNumber = 42; anEmployee.salary = 80000;
// Output the values of an employee.
11
Chapter 1
cout << “Employee: “ << anEmployee.firstInitial << anEmployee.middleInitial << anEmployee.lastInitial << endl;
cout << “Number: “ << anEmployee.employeeNumber << endl;
cout << “Salary: $” << anEmployee.salary << endl;
return 0;
}
Conditionals
Conditionals let you execute code based on whether or not something is true. There are three main types of conditionals in C++.
If/Else Statements
The most common conditional is the if statement, which can be accompanied by else. If the condition given inside the if statement is true, the line or block of code is executed. If not, execution continues to the else case if present, or to the code following the conditional. The following pseudocode shows a cascading if statement, a fancy way of saying that the if statement has an else statement that in turn has another if statement, and so on.
if (i > 4) {
//Do something.
}else if (i > 2) {
//Do something else.
}else {
//Do something else.
The expression between the parentheses of an if statement must be a Boolean value or evaluate to a Boolean value. Conditional operators, described below, provide ways of evaluating expressions to result in a true or false Boolean value.
Switch Statements
The switch statement is an alternate syntax for performing actions based on the value of a variable. In switch statements, the variable must be compared to a constant, so the greater-than if statements above could not be converted to switch statements. Each constant value represents a “case”. If the variable matches the case, the subsequent lines of code are executed until the break statement is reached. You can also provide a default case, which is matched if none of the other cases match.
switch statements are generally used when you want to do something based on the specific value of a variable, as opposed to some test on the variable. The following pseudocode shows a common use of the switch statement.
switch (menuItem) { case kOpenMenuItem:
// Code to open a file break;
12
A Crash Course in C++
case kSaveMenuItem:
// Code to save a file break;
default:
// Code to give an error message break;
}
If you omit the break statement, the code for the subsequent case will be executed whether or not it matches. This is sometimes useful, but more frequently a source of bugs.
The Ternary Operator
C++ has one operator that takes three arguments, known as the ternary operator. It is used as a shorthand conditional expression of the form “if [something] then [perform action], otherwise [perform some other action]”. The ternary operator is represented by a ? and a :. The following code will output “yes” if the variable i is greater than 2, and “no” otherwise.
std::cout << ((i > 2) ? “yes” : “no”);
The advantage of the ternary operator is that it can occur within almost any context. In the preceding example, the ternary operator is used within code that performs output. A convenient way to remember how the syntax is used is to treat the question mark as though the statement that comes before it really is a question. For example, “Is i greater than 2? If so, the result is ‘yes’: if not, the result is ‘no.’”
Unlike an if statement or a switch statement, the ternary operator doesn’t execute code based on the result. Instead, it is used within code, as shown in the preceding example. In this way, it really is an operator (like + and -) as opposed to a true conditional, such as if and switch.
Conditional Operators
You have already seen a conditional operator without a formal definition. The > operator compares two values. The result is “true” if the value on the left is greater than the value on the right. All conditional operators follow this pattern — they all result in a true or false.
The table below shows other common conditional operators.
Operator |
Description |
Usage |
|
|
|
< |
Determines if the left-hand side |
if (i <= 0) { |
<= |
is less than, less than or equal to, |
std::cout << “i is negative”; |
> |
greater than,or greater than or |
} |
>= |
equal to the right-hand side. |
|
== |
Determines if the left-hand side |
if (i == 3) { |
|
equals the right-hand side. |
std::cout << “i is 3”; |
|
Don’t confuse this with the |
} |
|
= (assignment) operator! |
|
|
|
|
|
|
Table continued on following page |
13