c++ eval - double numbers v1.0, C++ (vc++)

c++ eval - double numbers v1.0

#include <iostream>
#include <string>
#include <cmath>
using namespace std;

template<class T>
class Node {
public:
	T data;
	Node<T> *next;

Node() {
		data = 0;
		next = 0;
	}

Node(T value, Node<T> *nxt = 0) {
		data = value;
		next = nxt;
	}
};

template<class T>
class List {
private:
	Node<T> *head, *tail;

public:
	List() {
		head = tail = 0;
	}

int Count() {
		int s = 0;
		Node<T> *temp = head;
		while (temp != 0) {
			temp = temp->next;
			s++;
		}
		return s;
	}

void Add2Head(T value) {
		if (head == 0) {
			head = tail = new Node<T>(value, 0);
		}
		else {
			Node<T> *temp = new Node<T>(value, 0);
			temp->next = head;
			head = temp;
		}
	}

void DeleteHead(T &n) {
		if (head == 0) {
			return;
		}
		else if (head == tail) {
			n = (head->data);
			head = tail = 0;
		}
		else {
			n = (head->data);
			Node<T> *temp = head->next;
			delete head;
			head = temp;
		}
	}

void DeleteHead() {
		if (head == 0) {
			return;
		}
		else if (head == tail) {
			head = tail = 0;
		}
		else {
			Node<T> *temp = head->next;
			delete head;
			head = temp;
		}
	}

T GetHeadValue() {
		return (head->data);
	}

bool IsEmpty() {
		return (head == 0);
	}
    
    void Print() {
        cout << "*****" << endl;
        Node<T> *temp=head;
        while (temp!=0) {
            cout << temp->data << endl;
            temp=temp->next;
        }
        cout << "*****" << endl;
    }
};

template<class T>
class Stack {
private:
	List<T> l;

public:
	void Push(T n) {
		l.Add2Head(n);
	}

bool Pop(T &n) {
		if (l.IsEmpty()) {
			return false;
		}
		else {
			l.DeleteHead(n);
			return true;
		}
	}

bool IsEmpty() {
		return l.IsEmpty();
	}

bool Flush() {
		if (l.IsEmpty()) {
			return false;
		}
		else {
			while (!l.IsEmpty()) {
				l.DeleteHead();
			}
			return true;
		}
	}

T Top() {
		return (l.GetHeadValue());
	}
    
    void Print() {
        l.Print();
    }
};

double eval(string str) {
    char d;
    double m,n;
    Stack<double> s;
    int length=0;
    double result=0;
    bool is_right_point=false;
    for (int i=0;i<str.size();i++) {
        d=str[i];
        if (d>='0' && d<='9') {
            result += (d-'0')*pow(10,(is_right_point=true) ? (length--) : (length++));
        }
        else if (d=='.') {
            length=-1;
            is_right_point=true;
        }
        else if (d==' ') {
            is_right_point=false;
            s.Push(result);
            length=0;
            result=0;
        }
        else if (d=='+') {
            s.Pop(m);
            s.Pop(n);
            s.Push(m+n);
        }
        else if (d=='-') {
            s.Pop(m);
            s.Pop(n);
            s.Push(n-m);
        }
        else if (d=='*') {
            s.Pop(m);
            s.Pop(n);
            s.Push(m*n);
        }
        else if (d=='/') {
            s.Pop(m);
            s.Pop(n);
            s.Push(n/m);
        }
    }
    s.Print();
    return s.Top();
}

void main() {
    /*
	char str[] = "Hello World!";
	Stack s;
	cout << str << endl;
	for (int i = 0; i < sizeof(str); i++) {
		s.Push(str[i]);
	}

cout << endl;
	cout << s.IsEmpty() << endl;
	cout << s.Top() << endl;
    */
	//system("pause");
    cout << eval("9.2 2 + 5 +") << endl;
}


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