calculator.h

模拟计算器的实现

enum boolean{ false,true };
#include<math.h>
#include<stack.h>
#include<iostream.h>
class calculator{
public:
	calculator();//我认为书上的是不对的
	void run();
	void clear();
private:
	void addoperand( double value);
	boolean get2operands( double& left,double& right);
	void dooperator(char op);
	stack<double> s;
};


void calculator::addoperand(double value){
	s.push(value);
}

boolean calculator::get2operands(double& left,double& right){
	if(s.isempty()) {
		cerr<<"Missing operand!"<<endl; return false;
	}
	right=s.pop();
	if(s.isempty()){
		cerr<<"Missing operand!"<<endl; return false;
	}
	left=s.pop();
	return true;
}

void calculator::dooperator(char op){
	double left,right; boolean result;
	result=get2operands(letf,right);
	if(result==true)
		switch(op){
case'+': s.push(left+right); break;
case'-': s.push(left-right); break;
case'*': s.push(left*right); break;
case'/': if(right==0.0){
	cerr<<"Divide by 0!"<<endl; clear();
		 }
	else s.push(left/right); break;//和书上的不一样
case'^': s.push( pow(left,right) ); break;
	}
	else clear();
}


void calculator::run(){
	char ch; double newoperand;
	while(cin>>ch, ch!='='){
		switch(ch){
		case'+': case'-': case'*': case'/': case'^':
			dooperator(ch); break;
		default:  cin.putback(ch);
			cin>> newoperand;
			addopreand(newoperand);
			break;
		}
	}
}

void calculator::clear(){
	s.makeempty();
}