Question

我正在从编程：原理与实践使用C ++ / Edition 2学习c ++，而且我遇到了矢量问题。我使用了Stroustrup的书here提供的包含头文件。当我编译以下矢量程序时，我收到一个错误。

#include "std_lib_facilities.h"

int main()
{
    vector<int> v = {5, 7, 9, 4, 6, 8};
    for (int i=0; i<v.size(); ++i)
        cout << v[i] << endl;
}

错误

vector.cpp:5:21 error: no matching constructor for initialization of 'Vector<int>'
    vector<int> v = {5, 7, 9, 4, 6, 8};
                ^   ~~~~~~~~~~~~~~~~~~
./std_lib_facilities.h:82:5: note: candidate constructor template not viable: 
      requires 2 arguments, but 6 were provided
    Vector(I first, I last) :std::vector<T>(first, last) {}
    ^
./std_lib_facilities.h:79:14: note: candidate constructor not viable: requires 2 
      arguments but 6 were provided
    Vector(size_type n, const T& v) :std::vector<T>(n,v) {}
    ^
./std_lib_facilities.h:79:14: note: candidate constructor not viable: requires 
      single argument 'n', but 6 arguments were provided
    explicit Vector(size_type n) :std::vector<T>(n) {}
./std_lib_facilities.h:75:27: note: candidate constructor (the implicit move 
      constructor) not viable: requires 1 argument, but 6 were provided
    template< class T> struct Vector : public std::vector<T> {
                              ^
./std_lib_facilities.h:75:27: note: candidate constructor (the implicit copy 
  constructor) not viable: requires 1 argument but 6 were provided
./std_lib_facilities.h:78:5: note: candidate constructor not viable: requires 0 
      arguments, but 6 were provided
    Vector() { }
    ^

我正在编译：clang ++ -std = c ++ 11 -stdlib = libc ++ vector.cpp

当我查看我的Clang版本时，我得到：

Apple LLVM Version 8.0.0 (clang-800.0.42.1)
Target: x86_64-apple-darwin16.1.0
Thread model: posse
InstalledDir: /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin

我无法理解错误和警告，也不确定从何处开始。感谢您提供的任何见解。

Answer 1

std_lib_facilities.h将类Vector<T>定义为：

template< class T> struct Vector : public std::vector<T> {
    typedef typename std::vector<T>::size_type size_type;

    Vector() { }
    explicit Vector(size_type n) :std::vector<T>(n) {}
    Vector(size_type n, const T& v) :std::vector<T>(n,v) {}
    template <class I>
    Vector(I first, I last) :std::vector<T>(first,last) {}

    T& operator[](unsigned int i) // rather than return at(i);
    {
        if (i<0||this->size()<=i) throw Range_error(i);
        return std::vector<T>::operator[](i);
    }
    const T& operator[](unsigned int i) const
    {
        if (i<0||this->size()<=i) throw Range_error(i);
        return std::vector<T>::operator[](i);
    }
};

// disgusting macro hack to get a range checked vector:
#define vector Vector

如您所见，没有initializer_list构造函数。

此时，您的选择有限。

您可以使用std_lib_facilities.h
包括#undef vector

std_lib_facilities.h

您可以替换Vector类模板构造函数继承的构造函数（using vector<T>::vector;）：

template< class T> struct Vector : public std::vector<T> {
    typedef typename std::vector<T>::size_type size_type;

    using std::vector<T>::vector;

    T& operator[](unsigned int i) // rather than return at(i);
    {
        if (i<0||this->size()<=i) throw Range_error(i);
        return std::vector<T>::operator[](i);
    }
    const T& operator[](unsigned int i) const
    {
        if (i<0||this->size()<=i) throw Range_error(i);
        return std::vector<T>::operator[](i);
    }
};

Answer 2

链接的头文件包含以下行：

#define vector Vector

这意味着当你编写vector<int>时，编译器会看到Vector<int>，这是他自己的向量实现。我没有看到构造函数从硬编码数组构建实例，就像你想要做的那样。

如果包含实际的标准库，它应该可以工作，因为您在C ++ 11中进行编译（参见here）。虽然该向量不会在链接头文件中添加范围检查。

在Mac上没有用于初始化的匹配构造函数

2 个答案: