4elist2107.cpp

《21天学通C＋＋》附盘的原代码。书上的每个例子在这里都有相应的C语言程序。

enum LEVEL { NONE, LOW, MEDIUM, HIGH };
const int FALSE = 0;
const int TRUE = 1;
typedef int BOOL;

#define DEBUGLEVEL HIGH

#include <iostream.h>
#include <string.h>

#if DEBUGLEVEL < LOW  // must be medium or high
	#define ASSERT(x)
#else
	#define ASSERT(x) \
			if (! (x)) \
			{ \
			cout << "ERROR!! Assert " << #x << " failed\n"; \
			cout << " on line " << __LINE__  << "\n"; \
			cout << " in file " << __FILE__ << "\n";  \
			}
#endif

#if DEBUGLEVEL < MEDIUM
	#define EVAL(x)
#else
	#define EVAL(x) \
			cout << #x << ":\t" << x << endl;
#endif

#if DEBUGLEVEL < HIGH
	#define PRINT(x)
#else
	#define PRINT(x) \
			cout << x << endl;
#endif


class String
{
public:
	// constructors
	String();
	String(const char *const);
	String(const String &);
	~String();

	char & operator[](int offset);
	char operator[](int offset) const;

	String & operator= (const String &);
	int GetLen()const { return itsLen; }
	const char * GetString() const
		{ return itsString; }
	BOOL Invariants() const;

private:
	String (int);         // private constructor
	char * itsString;
	unsigned short itsLen;
};

// default constructor creates string of 0 bytes
String::String()
{
	itsString = new char[1];
	itsString[0] = '\0';
	itsLen=0;
	ASSERT(Invariants());
}

// private (helper) constructor, used only by
// class methods for creating a new string of
// required size.  Null filled.
String::String(int len)
{
	itsString = new char[len+1];
	for (int i = 0; i<=len; i++)
		itsString[i] = '\0';
	itsLen=len;
	ASSERT(Invariants());
}

// Converts a character array to a String
String::String(const char * const cString)
{
	itsLen = strlen(cString);
	itsString = new char[itsLen+1];
	for (int i = 0; i<itsLen; i++)
		itsString[i] = cString[i];
	itsString[itsLen]='\0';
	ASSERT(Invariants());
}

// copy constructor
String::String (const String & rhs)
{
	itsLen=rhs.GetLen();
	itsString = new char[itsLen+1];
	for (int i = 0; i<itsLen;i++)
		itsString[i] = rhs[i];
	itsString[itsLen] = '\0';
	ASSERT(Invariants());
}

// destructor, frees allocated memory
String::~String ()
{
	ASSERT(Invariants());
	delete [] itsString;
	itsLen = 0;
}

// operator equals, frees existing memory
// then copies string and size
String& String::operator=(const String & rhs)
{
	ASSERT(Invariants());
	if (this == &rhs)
		return *this;
	delete [] itsString;
	itsLen=rhs.GetLen();
	itsString = new char[itsLen+1];
	for (int i = 0; i<itsLen;i++)
		itsString[i] = rhs[i];
	itsString[itsLen] = '\0';
	ASSERT(Invariants());
	return *this;
}

//non constant offset operator
char & String::operator[](int offset)
{
	ASSERT(Invariants());
	if (offset > itsLen)
	{
		ASSERT(Invariants());
		return itsString[itsLen-1];
	}
	else
	{
		ASSERT(Invariants());
		return itsString[offset];
	}
}

// constant offset operator
char String::operator[](int offset) const
{
	ASSERT(Invariants());
	char retVal;
	if (offset > itsLen)
		retVal = itsString[itsLen-1];
	else
		retVal = itsString[offset];
	ASSERT(Invariants());
	return retVal;
}

BOOL String::Invariants() const
{
	PRINT("(String Invariants Checked)");
	return ((BOOL)(itsLen&&itsString)||(!itsLen&&!itsString));
}

class Animal
{
public:
	Animal():itsAge(1),itsName("John Q. Animal")
		{ASSERT(Invariants());}

	Animal(int, const String&);
	~Animal(){}

	int GetAge()
	{
		ASSERT(Invariants());
		return itsAge;
	}

	void SetAge(int Age)
	{
		ASSERT(Invariants());
		itsAge = Age;
		ASSERT(Invariants());
	}
	String& GetName()
	{
		ASSERT(Invariants());
		return itsName;
	}

	void SetName(const String& name)
	{
		ASSERT(Invariants());
		itsName = name;
		ASSERT(Invariants());
	}

	BOOL Invariants();
private:
	int itsAge;
	String itsName;
};

Animal::Animal(int age, const String& name):
	itsAge(age),
	itsName(name)
{
	ASSERT(Invariants());
}

BOOL Animal::Invariants()
{
	PRINT("(Animal Invariants Checked)");
	return (itsAge > 0 && itsName.GetLen());
}

int main()
{
	const int AGE = 5;
	EVAL(AGE);
	Animal sparky(AGE,"Sparky");
	cout << "\n" << sparky.GetName().GetString();
	cout << " is ";
	cout << sparky.GetAge() << " years old.";
	sparky.SetAge(8);
	cout << "\n" << sparky.GetName().GetString();
	cout << " is ";
	cout << sparky.GetAge() << " years old.";
	return 0;
}