我正在尝试编译C++ 之旅 中描述“抽象类型”的第 4.3 章中的代码。但是,我收到编译器错误:
$ g++ -std=c++11 abstract.cpp Vector.cpp Vector_container.cpp
/tmp/ccToFsNS.o: In function `g()':
abstract.cpp:(.text+0x9c): undefined reference to `Vector_container::Vector_container(std::initializer_list<double>)'
abstract.cpp:(.text+0xb4): undefined reference to `Vector_container::~Vector_container()'
abstract.cpp:(.text+0xc5): undefined reference to `Vector_container::~Vector_container()'
collect2: error: ld returned 1 exit status
我怎样才能修复我的代码以便它编译?我是 C++ 的新手,正在尝试尽我所能转录 Stroustrup 的示例。
抽象.cpp:
#include "Vector_container.hpp"
#include <iostream>
void use(Container& c)
{
const int sz = c.size();
for (auto i = 0; i != sz; ++i)
{
std::cout << c[i] << "\n";
}
}
void g()
{
Vector_container vc {10, 9, 8, 7, 6};
use(vc);
}
int main()
{
g();
}
Vector_container.hpp:
#include "Container.hpp"
#include "Vector.hpp"
#include <initializer_list>
#pragma once
class Vector_container : public Container {
Vector v;
public:
Vector_container(int);
Vector_container(std::initializer_list<double>);
~Vector_container();
double& operator[](int);
int size() const;
};
Vector_container.cpp:
#include "Container.hpp"
#include "Vector.hpp"
class Vector_container : public Container {
Vector v;
public:
Vector_container(int s) : v(s) {}
Vector_container(std::initializer_list<double> lst) : v{lst} {}
~Vector_container() {}
double& operator[](int i) { return v[i]; }
int size() const { return v.size(); }
};
容器.hpp:
#pragma once
class Container {
public:
virtual double& operator[](int) = 0;
virtual int size() const = 0;
virtual ~Container() {}
};
vector .hpp:
#include <initializer_list>
#pragma once
class Vector {
public:
Vector(int);
Vector(std::initializer_list<double>);
~Vector();
double& operator[](int);
int size() const;
void push_back(double);
private:
double* elem;
int sz;
};
vector .cpp:
#include "Vector.hpp"
#include <stdexcept>
Vector::Vector(int s) : elem{new double[s]}, sz{s}
{
if (s < 0)
{
throw std::length_error{"Size must be >= 0"};
}
for (auto i = 0; i != s; ++i)
{
elem[i] = 0;
}
}
Vector::Vector(std::initializer_list<double> lst)
: elem{new double[lst.size()]}, sz{static_cast<int>(lst.size())}
{
std::copy(lst.begin(), lst.end(), elem);
}
Vector::~Vector() {
delete[] elem;
}
double& Vector::operator[](int i)
{
if (i < 0 || size() <= i)
{
throw std::out_of_range{"Vector::operator[]"};
}
return elem[i];
}
int Vector::size() const
{
return sz;
}
最佳答案
正如评论者和 Sam 所指出的,我没有正确定义 Vector_container
。我将 Vector_container.cpp 更改为:
#include "Vector_container.hpp"
Vector_container::Vector_container(int s) : v(s) {}
Vector_container::Vector_container(std::initializer_list<double> lst) : v{lst} {}
Vector_container::~Vector_container() {}
double& Vector_container::operator[](int i)
{
return v[i];
}
int Vector_container::size() const
{
return v.size();
}
现在程序按预期编译和运行。
关于C++ 未定义对 `Vector_container::Vector_container(std::initializer_list<double>)' 的引用,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/33847833/