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[英]Calling another member function from a function in a class template in C++
[英]Symbol referencing errors from calling a member function of a template class
我正在編寫一個程序,該程序使用堆棧來評估從文件讀取的中綴表達式。 這是代碼:
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;
}
看起來一切正常,但是當我編譯它時,我收到此錯誤消息。
> 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
我已經能夠在infix文件的主目錄中將錯誤定位到push和pop成員函數的調用。 我嘗試在頭文件中像size函數一樣內聯定義它們,並且使用g ++ infix.cpp ptStack.h可以很好地進行編譯,但是當我運行它時遇到了分段錯誤。
有誰知道如何解決這些錯誤之一? 提前致謝。
只需使用g++
編譯所有.cpp文件
g++ ptStack.cpp infix.cpp
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