This question already has answers here:
Why can templates only be implemented in the header file?
（16个答案）
4年前关闭。
下面是我执行词法分析的代码。我有几个要求。
我收到LNK2019错误。 LNK2019未解决的外部符号
“公共：__ thiscall Stack :: Stack（void）”
函数中引用的（?? 0？$ Stack @ UToken @ LexicalAnalysis @@@@@ QAE @ XZ）
“公共：__thiscall LexicalAnalysis :: LexicalAnalysis（void）”
（?? 0LexicalAnalysis @@ QAE @ XZ）。我认为这与tokens变量及其在构造函数中的构造方式有关。不知道
请查看我的代码以查看我是否正确管理了内存，并且
看看我最初的解决方法是否正确。
--
（16个答案）
4年前关闭。
下面是我执行词法分析的代码。我有几个要求。
我收到LNK2019错误。 LNK2019未解决的外部符号
“公共：__ thiscall Stack :: Stack（void）”
函数中引用的（?? 0？$ Stack @ UToken @ LexicalAnalysis @@@@@ QAE @ XZ）
“公共：__thiscall LexicalAnalysis :: LexicalAnalysis（void）”
（?? 0LexicalAnalysis @@ QAE @ XZ）。我认为这与tokens变量及其在构造函数中的构造方式有关。不知道
请查看我的代码以查看我是否正确管理了内存，并且
看看我最初的解决方法是否正确。
--
// Stack.h
#pragma once
#include <iostream>
#include <string>
using namespace std;
template <typename T>
class Stack
{
public:
// Constructors
Stack();
Stack(const Stack<T>& rhs);
Stack(Stack<T>&& rhs);
// Destructor
~Stack();
// Helper Functions
inline int getSize() const
{
return size;
}
// Is the stack empty, no memory
inline bool isEmpty()
{
return (size == 0) ? true : false;
}
// Add an element to the stack
inline void push(const T& value)
{
if (size == capacity)
{
capacity = capacity ? capacity * 2 : 1;
T* dest = new T[capacity];
// Copy the contents of the old array into the new array
copy(data, data + size, dest);
delete[] data;
data = dest;
}
// Stack size is increased by 1
// Value is pushed
data[size++] = value;
}
// Add an element to the stack (rvalue ref) IS THIS RIGHT??
inline void push(const T&& value)
{
if (size == capacity)
{
capacity = capacity ? capacity * 2 : 1;
T* dest = new T[capacity];
// Copy the contents of the old array into the new array
copy(data, data + size, dest);
delete[] data;
data = dest;
}
// Stack size is increased by 1
// Value is pushed
data[size++] = value;
}
// Remove an element from the stack
inline const T& pop()
{
if (size > 0)
{
T value;
size--;
value = data[size];
T* dest = new T[size];
// Copy the contents of the old array into the new array
copy(data, data + (size), dest);
delete[] data;
data = dest;
return value;
}
return NULL;
}
// Search stack starting from TOP for x, return the first x found
T& operator[](unsigned int i)
{
return data[i];
}
T operator[](unsigned int i) const
{
return data[i];
}
private:
T* data;
size_t size, capacity;
};
// Stack.cpp
#include "Stack.h"
// Constructor
template <typename T>
Stack<T>::Stack()
{
data = nullptr;
size = 0;
capacity = 0;
}
// Copy Constructor
template <typename T>
Stack<T>::Stack(const Stack<T>& rhs)
{
this->size = rhs.size;
this->capacity = rhs.capacity;
this->data = new T[size];
for (int i = 0; i < size; i++)
{
data[i] = rhs.data[i];
}
}
// Move Constructor
template <typename T>
Stack<T>::Stack(Stack<T>&& rhs)
{
this->size = rhs.size;
this->capacity = rhs.capacity;
this->data = rhs.data;
rhs.data = nullptr;
}
// Destructor
template <typename T>
Stack<T>::~Stack()
{
delete[] data;
}
// LexicalAnalysis.h
#pragma once
#include <iostream>
#include <string>
#include "Stack.h"
#define NUM_KEYWORDS 3
#define NUM_REL_OP 6
#define NUM_OTHER_OP 2
using namespace std;
class LexicalAnalysis
{
public:
// Constructor
LexicalAnalysis();
// Destructor
~LexicalAnalysis();
// Methods
void createTokenStack(const string& inputString);
inline bool isAlpha(const char& ch) const
{
int asciiVal = ch;
if (((asciiVal >= 65) && (asciiVal <= 90)) ||
((asciiVal >= 97) && (asciiVal <= 122)))
return true;
return false;
}
inline bool isWord(const string& str) const
{
if (str.length() > 1)
return true;
return false;
}
inline bool isDigit(const char& ch) const
{
int asciiVal = ch;
if ((asciiVal >= 48) && (asciiVal <= 57))
return true;
return false;
}
inline bool isRelationalOperator(const char& ch) const
{
if (ch == '=' || ch == '<' || ch == '>')
return true;
return false;
}
inline bool isOtherOperator(const char& ch) const
{
if (ch == ',' || ch == '*')
return true;
return false;
}
inline void printTokenStack()
{
for (int i = 0; i < tokens->getSize(); i++)
{
cout << tokens[i][0].instance << endl;
}
}
private:
enum TokenType {
IDENTIFIER,
KEYWORD,
NUMBER,
REL_OP, // such as == < > =! => =<
OTHER_OP, // such as , *
UNDEF, // undefined
EOT // end of token
};
struct Token {
TokenType tokenType;
string instance;
};
Stack<Token>* tokens;
// Methods
void splitString(const string& inputString, Stack<string>& result);
};
// LexicalAnalysis.cpp
#include "LexicalAnalysis.h"
LexicalAnalysis::LexicalAnalysis()
{
tokens = new Stack<Token>();
}
LexicalAnalysis::~LexicalAnalysis()
{
}
void LexicalAnalysis::splitString(const string& inputString, Stack<string>& result)
{
const char delim[2] = { ',', ' ' };
char* dup = strdup(inputString.c_str());
char* token = strtok(dup, delim);
while (token != NULL)
{
result.push(string(token));
token = strtok(NULL, delim);
}
// ARE THESE DELETES NECESSARY?
delete dup;
delete token;
}
}
// main.cpp
#include <iostream>
#include <string>
#include "LexicalAnalysis.h"
using namespace std;
int main(int argv, char* argc)
{
LexicalAnalysis lex = LexicalAnalysis();
lex.createTokenStack("GET id, fname, lname FROM employee WHERE id > 5");
system("PAUSE");
}
最佳答案
问题是您在cpp文件中定义了Stack方法。所有模板代码都应放在头文件中。
模板定义必须在使用定义时可供编译器使用。因此，将模板代码放在stack.h文件中，而不是stack.cpp中，链接错误将消失。实际上，所有stack.cpp代码都应该在stack.h中，您可以完全摆脱stack.cpp。
关于第二个问题，您的pop方法确实很奇怪。为什么要在弹出窗口上分配内存？只需减小大小，就无需分配更多的内存。
inline const T& pop()
{
if (size == 0)
throw std::runtime_error("stack underflow");
return data[--size];
}