未在std_lib_facilities中声明的Cout

Question

我试图在代码中使用标题std_lib_facilities，但我认为我做错了一些事情，因为当我尝试使用以下代码时：

#include "../std_lib_facilities.h"
#include "stdafx.h"
int main()
{
    cout<<"Hello, World!\n";
    return 0;
}

它给了我这个错误

Error   C2065   'cout': undeclared identifier

我的std_lib_facilities在项目文件夹中，它在我的Visual 2015的header选项卡中。std_lib_facilities的代码如下：

/*
   std_lib_facilities.h
*/

/*
    simple "Programming: Principles and Practice using C++ (second edition)" course header to
    be used for the first few weeks.
    It provides the most common standard headers (in the global namespace)
    and minimal exception/error support.

    Students: please don't try to understand the details of headers just yet.
    All will be explained. This header is primarily used so that you don't have
    to understand every concept all at once.

    By Chapter 10, you don't need this file and after Chapter 21, you'll understand it

    Revised April 25, 2010: simple_error() added

    Revised November 25 2013: remove support for pre-C++11 compilers, use C++11: <chrono>
    Revised November 28 2013: add a few container algorithms
    Revised June 8 2014: added #ifndef to workaround Microsoft C++11 weakness
*/

#ifndef H112
#define H112 251113L


#include<iostream>
#include<iomanip>
#include<fstream>
#include<sstream>
#include<cmath>
#include<cstdlib>
#include<string>
#include<list>
#include <forward_list>
#include<vector>
#include<unordered_map>
#include<algorithm>
#include <array>
#include <regex>
#include<random>
#include<stdexcept>

//------------------------------------------------------------------------------


//------------------------------------------------------------------------------

typedef long Unicode;

//------------------------------------------------------------------------------

using namespace std;

template<class T> string to_string(const T& t)
{
    ostringstream os;
    os << t;
    return os.str();
}

struct Range_error : out_of_range { // enhanced vector range error reporting
    int index;
    Range_error(int i) :out_of_range("Range error: "+to_string(i)), index(i) { }
};


// trivially range-checked vector (no iterator checking):
template< class T> struct Vector : public std::vector<T> {
    using size_type = typename std::vector<T>::size_type;

#ifdef _MSC_VER
    // microsoft doesn't yet support C++11 inheriting constructors
    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) {}
    Vector(initializer_list<T> list) : std::vector<T>(list) {}
#else
    using std::vector<T>::vector;   // inheriting constructor
#endif

    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

// trivially range-checked string (no iterator checking):
struct String : std::string {
    using size_type = std::string::size_type;
//  using string::string;

    char& operator[](unsigned int i) // rather than return at(i);
    {
        if (i<0||size()<=i) throw Range_error(i);
        return std::string::operator[](i);
    }

    const char& operator[](unsigned int i) const
    {
        if (i<0||size()<=i) throw Range_error(i);
        return std::string::operator[](i);
    }
};


namespace std {

    template<> struct hash<String>
    {
        size_t operator()(const String& s) const
        {
            return hash<std::string>()(s);
        }
    };

} // of namespace std


struct Exit : runtime_error {
    Exit(): runtime_error("Exit") {}
};

// error() simply disguises throws:
inline void error(const string& s)
{
    throw runtime_error(s);
}

inline void error(const string& s, const string& s2)
{
    error(s+s2);
}

inline void error(const string& s, int i)
{
    ostringstream os;
    os << s <<": " << i;
    error(os.str());
}


template<class T> char* as_bytes(T& i)  // needed for binary I/O
{
    void* addr = &i;    // get the address of the first byte
                        // of memory used to store the object
    return static_cast<char*>(addr); // treat that memory as bytes
}


inline void keep_window_open()
{
    cin.clear();
    cout << "Please enter a character to exit\n";
    char ch;
    cin >> ch;
    return;
}

inline void keep_window_open(string s)
{
    if (s=="") return;
    cin.clear();
    cin.ignore(120,'\n');
    for (;;) {
        cout << "Please enter " << s << " to exit\n";
        string ss;
        while (cin >> ss && ss!=s)
            cout << "Please enter " << s << " to exit\n";
        return;
    }
}



// error function to be used (only) until error() is introduced in Chapter 5:
inline void simple_error(string s)  // write ``error: s and exit program
{
    cerr << "error: " << s << '\n';
    keep_window_open();     // for some Windows environments
    exit(1);
}

// make std::min() and std::max() accessible on systems with antisocial macros:
#undef min
#undef max


// run-time checked narrowing cast (type conversion). See ???.
template<class R, class A> R narrow_cast(const A& a)
{
    R r = R(a);
    if (A(r)!=a) error(string("info loss"));
    return r;
}

// random number generators. See 24.7.



inline int randint(int min, int max) { static default_random_engine ran; return uniform_int_distribution<>{min, max}(ran); }

inline int randint(int max) { return randint(0, max); }

//inline double sqrt(int x) { return sqrt(double(x)); } // to match C++0x

// container algorithms. See 21.9.

template<typename C>
using Value_type = typename C::value_type;

template<typename C>
using Iterator = typename C::iterator;

template<typename C>
    // requires Container<C>()
void sort(C& c)
{
    std::sort(c.begin(), c.end());
}

template<typename C, typename Pred>
// requires Container<C>() && Binary_Predicate<Value_type<C>>()
void sort(C& c, Pred p)
{
    std::sort(c.begin(), c.end(), p);
}

template<typename C, typename Val>
    // requires Container<C>() && Equality_comparable<C,Val>()
Iterator<C> find(C& c, Val v)
{
    return std::find(c.begin(), c.end(), v);
}

template<typename C, typename Pred>
// requires Container<C>() && Predicate<Pred,Value_type<C>>()
Iterator<C> find_if(C& c, Pred p)
{
    return std::find_if(c.begin(), c.end(), p);
}

#endif //H112

有人知道我做错了什么吗？

Answer 1

我看到您在../std_lib_facilities.h之前就包含了stdafx.h。让我们考虑一下stdafx.h是什么。这是一个预编译标头。

H是一个由向导生成的文件，它描述了标准系统和特定于项目的文件，包括经常使用但很少更改的文件。 兼容编译器(例如VisualVISUAL6.0及更新版本)将预编译此文件，以减少整个编译时间。Visual C++ 将不会在源文件中包含"stdafx.h"之前编译任何内容，除非未选中编译选项/Yu'stdafx.h‘(默认情况下)；它假定源代码中的所有代码都已经编译完毕，并包括该行。

如果没有编译包含标准标头的部分，则会得到缺少声明的错误。

解决方案:将stdafx.h包含在文件的顶部，或者根本不使用预编译头，或者确保未选中适当的选项。

Answer 2

将using std::cout;或using namespace std;放入包含main ()函数的文件中。或者只是在cout的每一次求爱前加上std::。