一个小的计算器的实现

在假期间我写了一个用于计算表达式的C++类，终于明白了计算器的基本工作原理。以下是相关的代码，共有三个文件，分别是源文件，头文件和栈模板类头文件。

//Expression.cpp

#include "Expression.h"
#include 
#include 
using namespace std;
#define InitError \
	this->error=new string[error]; \
	this->error[0]="Error 0:A Number Divided By Zero."; \
	this->error[1]="Error 1:Null Value."; \
	this->error[2]="Error 2:Unknown Char.";	\
	this->error[3]="Error 3:Symbol After Symbol."; \
	this->error[4]="Error 4:\'.\' After \'.\'";
Expression::Expression(int max,char depart,int error)
:stack(max),num(max),depart(depart)
{
	InitError
}
Expression::~Expression()
{
	if(error)
		delete [] error;
}
Expression::Expression(string str,int max,char depart,int error)
:stack(max),num(max),depart(depart),str(str)
{
	InitError
}
#undef InitError
void Expression::ReadString(string str)
{
	this->str=str;
}
void Expression::Reset(int max)
{
	stack.Reset(max);
	stack.Clear();
	num.Reset(max);
	num.Clear();
}
inline bool Expression::Issymbol(char ch)//是否为运算符号
{
	return ch=='*'||ch=='/'||ch=='^'||ch=='+'||ch=='-';
}
inline bool Expression::Isnum(char ch)//是否为数字或者小数点
{
	return (ch>='0'&&ch<='9')||ch=='.';
}
inline bool Expression::Over(char ch1,char ch2)//运算符的优先级的判断
{
	if(ch1=='(')
		if(ch2=='(')
			return false;
		else
			return true;
	if(ch1=='^')
		if(ch2=='^')
			return false;
		else
			return true;
	if(ch1=='*'||ch1=='/')
		if(ch2=='+'||ch2=='-')
			return true;
	return false;
}
double Expression::Caculate1()//result保存了后缀表达式的值
{
	try
	{
		PreRead();
	}
	catch(string e)
	{
		throw(e);
	}
	result=0;
	behind="";
	int max=str.length();
	stack.Clear();
	for(int i=0;i

//Expression.h

#ifndef _Expression_h_
#define _Expression_h_
#define _stack_max_ 10	//这里规定了递归的深度，太小程序会出现内存错误
						//太大会浪费较多内存
#include 
#include 
using namespace std;
#include "stack.h"
class Expression
{
public:
	Expression(int max=_stack_max_,char depart='#',int error=5);
	Expression(string str,int max=_stack_max_,char depart='#',int error=5);
	virtual ~Expression();
	void ReadString(string str);
	void Reset(int max);
	double Caculate1();
	double GetResult();
	string GetBehind();
protected:
	virtual void LoadSymbol();//此函数必须在子类中重写
	virtual void PreRead();//此函数可以不用在子类中重写
	inline virtual bool Issymbol(char ch);//这里应与LadSymbol()中的符号对应
	inline bool Over(char ch1,char ch2);
	inline bool Isnum(char ch);
	inline double StrToDouble(string str);
	char depart;
	string str;
	string behind;
	string *error;
	double result;
	CStack stack;
	CStack num;
};
#endif

//stack.h

#ifndef _Stack_h_
#define _Stack_h_
template
class CStack
{
public:
	CStack(int max);
	CStack(CStack &temp);
	~CStack();
	bool IsEmpty();
	bool IsFull();
	bool Push(T temp);
	T& Popup();
	T Top();
	void Clear();
	void Reset(int max);
	int GetMax();
private:
	int max;
	int top;
	T* stack;
};

template
CStack::CStack(int max)
{
	this->max=max;
	top=-1;
	stack=new T[max];
}
template
CStack::CStack(CStack &temp):max(temp.max),top(temp.top)
{
	stack=new T[max];
	for(int i=0;i<=top;i++)
		stack[i]=temp.stack[i];
}
template
CStack::~CStack()
{
	if(stack)
		delete [] stack;
}
template
bool CStack::IsEmpty()
{
	return (top<0||top>=max);
}
template
bool CStack::IsFull()
{
	return top==max-1;
}
template
bool CStack::Push(T temp)
{
	if(IsFull())
		return false;
	stack[++top]=temp;
	return true;
}
template
T& CStack::Popup()
{
	return stack[top--];
}
template
void CStack::Clear()
{
	top=-1;
}
template
void CStack::Reset(int max)
{
	if(this->max>=max)
		return;
	T* temp=new T[max];
	for(int i=0;i<=top;i++)
		temp[i]=stack[i];
	this->max=max;
	delete [] stack;
	stack=temp;
}
template
T CStack::Top()
{
	return stack[top];
}
template
int CStack::GetMax()
{
	return max;
}
#endif