如何声明放在main之后的类模板？(How do I declare a class template that is placed after the main?)

 我正在尝试实现一个堆栈模板类。 但我想在主要之前宣布它。 我能这样做吗？ 我知道如果你把模型放在模板之后它会编译但是有可能先将主要的模板放入模板吗？ 
 
#include <iostream>


//start declaration of template
template <class T>
class stack<T>;
//end declaration of template
int main() {

    stack<char> s(5);
    s.push('a');
    s.push('b');
    cout <<s.pop()<<endl;
    stack<double> s1(10);
    s1.push(3.2);
    s1.push(0.5);
    cout << s1.pop()<<endl;

    return 0;
}


template <class T>
class stack {
    T *s;
    int size; //How many elements I can stole.
    int top; //Where the index is available.

public: 

    stack(int sz) {
        size = sz;
        s = new T[sz];
        top=-1;
    }

    void push(T e);
    T pop() {

        return s[top--];
    }
};



template <class T>
void stack<T>::push(T e) {

        s[++top] = e;
    }
 
 错误给出： 
 
1>.\classTemplPers.cpp(6) : error C2143: syntax error : missing ';' before '<'
1>.\classTemplPers.cpp(6) : error C2059: syntax error : '<'
 
 为了记录，这样做： 
 
template <class T>
class stack;
 
 也不起作用。 我看到这样的错误： 
 
1>.\classTemplPers.cpp(10) : error C2079: 's' uses undefined class 'stack<T>'

I am trying to implement a template class that is stack. But I want to declare it before main. Can I do that? I know it will compile if you put the main after the template but is it possible to put the main first then the template?
 
#include <iostream>


//start declaration of template
template <class T>
class stack<T>;
//end declaration of template
int main() {

    stack<char> s(5);
    s.push('a');
    s.push('b');
    cout <<s.pop()<<endl;
    stack<double> s1(10);
    s1.push(3.2);
    s1.push(0.5);
    cout << s1.pop()<<endl;

    return 0;
}


template <class T>
class stack {
    T *s;
    int size; //How many elements I can stole.
    int top; //Where the index is available.

public: 

    stack(int sz) {
        size = sz;
        s = new T[sz];
        top=-1;
    }

    void push(T e);
    T pop() {

        return s[top--];
    }
};



template <class T>
void stack<T>::push(T e) {

        s[++top] = e;
    }
 
Error given: 
 
1>.\classTemplPers.cpp(6) : error C2143: syntax error : missing ';' before '<'
1>.\classTemplPers.cpp(6) : error C2059: syntax error : '<'
 
For the record, doing this:
 
template <class T>
class stack;
 
doesn't work either. I see errors like this: 
 
1>.\classTemplPers.cpp(10) : error C2079: 's' uses undefined class 'stack<T>'

原文：https://stackoverflow.com/questions/36713412