符号引用调用模板类的成员函数时的错误

Question

我正在编写一个程序，它使用堆栈来评估从文件中读入的中缀表达式。这是代码：

ptStack.h

#ifndef STACK
#define STACK

#include <cstdlib>
#include <iostream>
using namespace std;

template <class Item>
class Stack
{
public:
    // CONSTRUCTOR
    Stack( ) {top = NULL; count = 0;}       // Inline

    // MODIFIER MEMBER FUNCTIONS
    void push( const Item& entry);
    Item pop( );

    // CONSTANT MEMBER FUNCTIONS
    int size( ) {return count;}             // Inline
    bool is_empty( ) {return count == 0;}   // Inline

private:
    // DATA MEMBERS
    struct Node
    {
        Item element;
        Node *next;
    };
    Node *top;
    int count;
};
#endif

ptStack.cpp

    #include <cassert>
#include "ptStack.h"
using namespace std;

// MODIFIER MEMBER FUNCTIONS
template <class Item> 
void Stack<Item>::push(const Item& entry)
{
    Node *temp;
    temp = new Node;
    temp->element = entry;
    temp->next = top->next;
    top->next = temp;
    count++;
}

template <class Item> 
Item Stack<Item>::pop( )
{
    Item value;
    Node *temp;
    value = top->next->element;
    temp = top->next;
    top->next = top->next->next;
    delete temp;
    count--;

    return value;
}

infix.cpp

#include <iostream>
#include <fstream>
#include <cstdlib>
#include "ptStack.h"
using namespace std;

// PRECONDITION: op must be an operator
// POSTCONDITION: returns precedence of operator
int pr(char op)
{
    int precedence = 0;
    switch (op)
    {
        case '+':
        case '-': precedence = 1;
        case '*':
        case '/': precedence = 2;
        default : precedence = 0;
    }
    return precedence;
}

// PRECONDITIONS: optr is one of the following: + - * /
//                opnd1 and opnd2 are numbers from 1-9
// POSTCONDITIONS: returns the result of the chosen mathematical operation
int apply(char optr, int opnd1, int opnd2)
{
    int result;
    switch (optr)
    {
        case '+': result = opnd2+opnd1;
        case '-': result = opnd2-opnd1;
        case '*': result = opnd2*opnd1;
        default : result = opnd2/opnd1;
    }
    return result;
}

int main()
{
    Stack<int> numbers;
    Stack<char> operators;
    char ch, optr;
    int num, opnd1, opnd2, prec = 0, newprec;
    ifstream in_file;                   // input file
    char in_file_name[20];              // name of input file (20 letter max)

    cout << "Enter input file name: ";
    cin >> in_file_name;
    in_file.open(in_file_name);         // opens file to read equations

    while (!in_file.eof())
    {
            cout << "Expression: ";

    while(in_file >> ch)
    {
        if (ch == ' ')
        {}
        else
        {
            num = ch - '0';
            if((num < 10) && (num > 0))
            {
                cout << num << " ";
                numbers.push(num);
            }
            else if((ch == '+') || (ch == '-') || (ch == '*') || (ch == '/'))
            {
                cout << ch << " ";
                newprec = pr(ch);
                if(newprec >= prec)
                {
                    prec = newprec;
                    operators.push(ch);
                }
                else if(newprec < prec)
                {
                    optr = operators.pop( );
                    opnd1 = numbers.pop( );
                    opnd2 = numbers.pop( );
                    num = apply(optr, opnd1, opnd2);
                    numbers.push(num);
                    operators.push(ch);
                }
            }
        }
        if(in_file.peek() == '\n')
            break;
    }

    num = operators.size();
    while(num != 0)
    {
        optr = operators.pop( );
        opnd1 = numbers.pop( );
        opnd2 = numbers.pop( );
        num = apply(optr, opnd1, opnd2);
        numbers.push(num);

        num = operators.size( );
    }
    num = numbers.pop( );
    cout << endl << "Value = " << num << endl << endl; 
    }

    return 0;
}

看起来一切都应该有效，但是当我编译它时，我收到此错误消息。

> g++ -c ptStack.cpp
> g++ infix.cpp ptStack.o

Undefined                       first referenced
 symbol                             in file
_ZN5StackIcE4pushERKc               /var/tmp//ccwhfRAZ.o
_ZN5StackIiE4pushERKi               /var/tmp//ccwhfRAZ.o
_ZN5StackIcE3popEv                  /var/tmp//ccwhfRAZ.o
_ZN5StackIiE3popEv                  /var/tmp//ccwhfRAZ.o
ld: fatal: symbol referencing errors. No output written to a.out

我已经能够确定中缀文件主要部分中push和pop成员函数调用的错误。我尝试在头文件中内联定义它们就像size函数一样，它使用g ++ infix.cpp ptStack.h编译得很好，但是当我运行它时会出现分段错误。

有谁知道如何修复这些错误？提前谢谢。

Answer 1

只需使用g++

编译所有.cpp文件

g++ ptStack.cpp infix.cpp