c++: std::endl 和操作符编译错误>>

Question

我正在编写一段简单的 c++ 代码来打印输入，直到输入不是 42。这是我的代码:

#include <iostream>

using namespace std;

int main(){
    while(true){
        int inp;
        cin >> inp >> endl;
        if(inp == 42){
            break;
        }
        cout << inp << endl;
    }
    return 0;
}

但是，当我编译它时，我得到一个错误列表:

testlife.cpp: In function ‘int main()’:
testlife.cpp:9:14: error: no match for ‘operator>>’ (operand types are ‘std::basic_istream<char>::__istream_type {aka std::basic_istream<char>}’ and ‘<unresolved overloaded function type>’)
   cin >> inp >> endl;
   ~~~~~~~~~~~^~~~~~~
In file included from /usr/include/c++/6/iostream:40:0,
                 from testlife.cpp:2:
/usr/include/c++/6/istream:120:7: note: candidate: std::basic_istream<_CharT, _Traits>::__istream_type& std::basic_istream<_CharT, _Traits>::operator>>(std::basic_istream<_CharT, _Traits>::__istream_type& (*)(std::basic_istream<_CharT, _Traits>::__istream_type&)) [with _CharT = char; _Traits = std::char_traits<char>; std::basic_istream<_CharT, _Traits>::__istream_type = std::basic_istream<char>]
       operator>>(__istream_type& (*__pf)(__istream_type&))
       ^~~~~~~~
/usr/include/c++/6/istream:120:7: note:   no known conversion for argument 1 from ‘<unresolved overloaded function type>’ to ‘std::basic_istream<char>::__istream_type& (*)(std::basic_istream<char>::__istream_type&) {aka std::basic_istream<char>& (*)(std::basic_istream<char>&)}’
/usr/include/c++/6/istream:124:7: note: candidate: std::basic_istream<_CharT, _Traits>::__istream_type& std::basic_istream<_CharT, _Traits>::operator>>(std::basic_istream<_CharT, _Traits>::__ios_type& (*)(std::basic_istream<_CharT, _Traits>::__ios_type&)) [with _CharT = char; _Traits = std::char_traits<char>; std::basic_istream<_CharT, _Traits>::__istream_type = std::basic_istream<char>; std::basic_istream<_CharT, _Traits>::__ios_type = std::basic_ios<char>]
       operator>>(__ios_type& (*__pf)(__ios_type&))
       ^~~~~~~~
/usr/include/c++/6/istream:124:7: note:   no known conversion for argument 1 from ‘<unresolved overloaded function type>’ to ‘std::basic_istream<char>::__ios_type& (*)(std::basic_istream<char>::__ios_type&) {aka std::basic_ios<char>& (*)(std::basic_ios<char>&)}’
/usr/include/c++/6/istream:131:7: note: candidate: std::basic_istream<_CharT, _Traits>::__istream_type& std::basic_istream<_CharT, _Traits>::operator>>(std::ios_base& (*)(std::ios_base&)) [with _CharT = char; _Traits = std::char_traits<char>; std::basic_istream<_CharT, _Traits>::__istream_type = std::basic_istream<char>]
       operator>>(ios_base& (*__pf)(ios_base&))
       ^~~~~~~~
/usr/include/c++/6/istream:131:7: note:   no known conversion for argument 1 from ‘<unresolved overloaded function type>’ to ‘std::ios_base& (*)(std::ios_base&)’
/usr/include/c++/6/istream:168:7: note: candidate: std::basic_istream<_CharT, _Traits>::__istream_type& std::basic_istream<_CharT, _Traits>::operator>>(bool&) [with _CharT = char; _Traits = std::char_traits<char>; std::basic_istream<_CharT, _Traits>::__istream_type = std::basic_istream<char>]
       operator>>(bool& __n)
       ^~~~~~~~
/usr/include/c++/6/istream:168:7: note:   no known conversion for argument 1 from ‘<unresolved overloaded function type>’ to ‘bool&’
/usr/include/c++/6/istream:172:7: note: candidate: std::basic_istream<_CharT, _Traits>& std::basic_istream<_CharT, _Traits>::operator>>(short int&) [with _CharT = char; _Traits = std::char_traits<char>]
       operator>>(short& __n);
       ^~~~~~~~
/usr/include/c++/6/istream:172:7: note:   no known conversion for argument 1 from ‘<unresolved overloaded function type>’ to ‘short int&’
/usr/include/c++/6/istream:175:7: note: candidate: std::basic_istream<_CharT, _Traits>::__istream_type& std::basic_istream<_CharT, _Traits>::operator>>(short unsigned int&) [with _CharT = char; _Traits = std::char_traits<char>; std::basic_istream<_CharT, _Traits>::__istream_type = std::basic_istream<char>]
       operator>>(unsigned short& __n)
       ^~~~~~~~
/usr/include/c++/6/istream:175:7: note:   no known conversion for argument 1 from ‘<unresolved overloaded function type>’ to ‘short unsigned int&’
/usr/include/c++/6/istream:179:7: note: candidate: std::basic_istream<_CharT, _Traits>& std::basic_istream<_CharT, _Traits>::operator>>(int&) [with _CharT = char; _Traits = std::char_traits<char>]
       operator>>(int& __n);
       ^~~~~~~~
/usr/include/c++/6/istream:179:7: note:   no known conversion for argument 1 from ‘<unresolved overloaded function type>’ to ‘int&’
/usr/include/c++/6/istream:182:7: note: candidate: std::basic_istream<_CharT, _Traits>::__istream_type& std::basic_istream<_CharT, _Traits>::operator>>(unsigned int&) [with _CharT = char; _Traits = std::char_traits<char>; std::basic_istream<_CharT, _Traits>::__istream_type = std::basic_istream<char>]
       operator>>(unsigned int& __n)
       ^~~~~~~~
/usr/include/c++/6/istream:182:7: note:   no known conversion for argument 1 from ‘<unresolved overloaded function type>’ to ‘unsigned int&’
/usr/include/c++/6/istream:186:7: note: candidate: std::basic_istream<_CharT, _Traits>::__istream_type& std::basic_istream<_CharT, _Traits>::operator>>(long int&) [with _CharT = char; _Traits = std::char_traits<char>; std::basic_istream<_CharT, _Traits>::__istream_type = std::basic_istream<char>]
       operator>>(long& __n)
       ^~~~~~~~
/usr/include/c++/6/istream:186:7: note:   no known conversion for argument 1 from ‘<unresolved overloaded function type>’ to ‘long int&’
/usr/include/c++/6/istream:190:7: note: candidate: std::basic_istream<_CharT, _Traits>::__istream_type& std::basic_istream<_CharT, _Traits>::operator>>(long unsigned int&) [with _CharT = char; _Traits = std::char_traits<char>; std::basic_istream<_CharT, _Traits>::__istream_type = std::basic_istream<char>]
       operator>>(unsigned long& __n)
       ^~~~~~~~
/usr/include/c++/6/istream:190:7: note:   no known conversion for argument 1 from ‘<unresolved overloaded function type>’ to ‘long unsigned int&’
/usr/include/c++/6/istream:195:7: note: candidate: std::basic_istream<_CharT, _Traits>::__istream_type& std::basic_istream<_CharT, _Traits>::operator>>(long long int&) [with _CharT = char; _Traits = std::char_traits<char>; std::basic_istream<_CharT, _Traits>::__istream_type = std::basic_istream<char>]
       operator>>(long long& __n)
       ^~~~~~~~
/usr/include/c++/6/istream:195:7: note:   no known conversion for argument 1 from ‘<unresolved overloaded function type>’ to ‘long long int&’
/usr/include/c++/6/istream:199:7: note: candidate: std::basic_istream<_CharT, _Traits>::__istream_type& std::basic_istream<_CharT, _Traits>::operator>>(long long unsigned int&) [with _CharT = char; _Traits = std::char_traits<char>; std::basic_istream<_CharT, _Traits>::__istream_type = std::basic_istream<char>]
       operator>>(unsigned long long& __n)
       ^~~~~~~~
/usr/include/c++/6/istream:199:7: note:   no known conversion for argument 1 from ‘<unresolved overloaded function type>’ to ‘long long unsigned int&’
/usr/include/c++/6/istream:214:7: note: candidate: std::basic_istream<_CharT, _Traits>::__istream_type& std::basic_istream<_CharT, _Traits>::operator>>(float&) [with _CharT = char; _Traits = std::char_traits<char>; std::basic_istream<_CharT, _Traits>::__istream_type = std::basic_istream<char>]
       operator>>(float& __f)
       ^~~~~~~~
/usr/include/c++/6/istream:214:7: note:   no known conversion for argument 1 from ‘<unresolved overloaded function type>’ to ‘float&’
/usr/include/c++/6/istream:218:7: note: candidate: std::basic_istream<_CharT, _Traits>::__istream_type& std::basic_istream<_CharT, _Traits>::operator>>(double&) [with _CharT = char; _Traits = std::char_traits<char>; std::basic_istream<_CharT, _Traits>::__istream_type = std::basic_istream<char>]
       operator>>(double& __f)
       ^~~~~~~~
/usr/include/c++/6/istream:218:7: note:   no known conversion for argument 1 from ‘<unresolved overloaded function type>’ to ‘double&’
/usr/include/c++/6/istream:222:7: note: candidate: std::basic_istream<_CharT, _Traits>::__istream_type& std::basic_istream<_CharT, _Traits>::operator>>(long double&) [with _CharT = char; _Traits = std::char_traits<char>; std::basic_istream<_CharT, _Traits>::__istream_type = std::basic_istream<char>]
       operator>>(long double& __f)
       ^~~~~~~~
/usr/include/c++/6/istream:222:7: note:   no known conversion for argument 1 from ‘<unresolved overloaded function type>’ to ‘long double&’
/usr/include/c++/6/istream:235:7: note: candidate: std::basic_istream<_CharT, _Traits>::__istream_type& std::basic_istream<_CharT, _Traits>::operator>>(void*&) [with _CharT = char; _Traits = std::char_traits<char>; std::basic_istream<_CharT, _Traits>::__istream_type = std::basic_istream<char>]
       operator>>(void*& __p)
       ^~~~~~~~
/usr/include/c++/6/istream:235:7: note:   no known conversion for argument 1 from ‘<unresolved overloaded function type>’ to ‘void*&’
/usr/include/c++/6/istream:259:7: note: candidate: std::basic_istream<_CharT, _Traits>& std::basic_istream<_CharT, _Traits>::operator>>(std::basic_istream<_CharT, _Traits>::__streambuf_type*) [with _CharT = char; _Traits = std::char_traits<char>; std::basic_istream<_CharT, _Traits>::__streambuf_type = std::basic_streambuf<char>]
       operator>>(__streambuf_type* __sb);
       ^~~~~~~~
/usr/include/c++/6/istream:259:7: note:   no known conversion for argument 1 from ‘<unresolved overloaded function type>’ to ‘std::basic_istream<char>::__streambuf_type* {aka std::basic_streambuf<char>*}’
In file included from /usr/include/c++/6/string:53:0,
                 from /usr/include/c++/6/bits/locale_classes.h:40,
                 from /usr/include/c++/6/bits/ios_base.h:41,
                 from /usr/include/c++/6/ios:42,
                 from /usr/include/c++/6/ostream:38,
                 from /usr/include/c++/6/iostream:39,
                 from testlife.cpp:2:
/usr/include/c++/6/bits/basic_string.tcc:1437:5: note: candidate: template<class _CharT, class _Traits, class _Alloc> std::basic_istream<_CharT, _Traits>& std::operator>>(std::basic_istream<_CharT, _Traits>&, std::__cxx11::basic_string<_CharT, _Traits, _Alloc>&)
     operator>>(basic_istream<_CharT, _Traits>& __in,
     ^~~~~~~~
/usr/include/c++/6/bits/basic_string.tcc:1437:5: note:   template argument deduction/substitution failed:
testlife.cpp:9:17: note:   couldn't deduce template parameter ‘_Alloc’
   cin >> inp >> endl;
                 ^~~~
In file included from /usr/include/c++/6/iostream:40:0,
                 from testlife.cpp:2:
/usr/include/c++/6/istream:799:5: note: candidate: std::basic_istream<_CharT2, _Traits2>& std::operator>>(std::basic_istream<_CharT2, _Traits2>&, _CharT2*) [with _CharT2 = char; _Traits2 = std::char_traits<char>; _CharT = char; _Traits = std::char_traits<char>]
     operator>>(basic_istream<char>& __in, char* __s);
     ^~~~~~~~
/usr/include/c++/6/istream:799:5: note:   no known conversion for argument 2 from ‘<unresolved overloaded function type>’ to ‘char*’
In file included from /usr/include/c++/6/istream:934:0,
                 from /usr/include/c++/6/iostream:40,
                 from testlife.cpp:2:
/usr/include/c++/6/bits/istream.tcc:923:5: note: candidate: std::basic_istream<_CharT, _Traits>& std::operator>>(std::basic_istream<_CharT, _Traits>&, _CharT&) [with _CharT = char; _Traits = std::char_traits<char>]
     operator>>(basic_istream<_CharT, _Traits>& __in, _CharT& __c)
     ^~~~~~~~
/usr/include/c++/6/bits/istream.tcc:923:5: note:   no known conversion for argument 2 from ‘<unresolved overloaded function type>’ to ‘char&’
In file included from /usr/include/c++/6/iostream:40:0,
                 from testlife.cpp:2:
/usr/include/c++/6/istream:756:5: note: candidate: template<class _Traits> std::basic_istream<char, _Traits>& std::operator>>(std::basic_istream<char, _Traits>&, unsigned char&)
     operator>>(basic_istream<char, _Traits>& __in, unsigned char& __c)
     ^~~~~~~~
/usr/include/c++/6/istream:756:5: note:   template argument deduction/substitution failed:
testlife.cpp:9:17: note:   cannot convert ‘std::endl’ (type ‘<unresolved overloaded function type>’) to type ‘unsigned char&’
   cin >> inp >> endl;
                 ^~~~
In file included from /usr/include/c++/6/iostream:40:0,
                 from testlife.cpp:2:
/usr/include/c++/6/istream:761:5: note: candidate: template<class _Traits> std::basic_istream<char, _Traits>& std::operator>>(std::basic_istream<char, _Traits>&, signed char&)
     operator>>(basic_istream<char, _Traits>& __in, signed char& __c)
     ^~~~~~~~
/usr/include/c++/6/istream:761:5: note:   template argument deduction/substitution failed:
testlife.cpp:9:17: note:   cannot convert ‘std::endl’ (type ‘<unresolved overloaded function type>’) to type ‘signed char&’
   cin >> inp >> endl;
                 ^~~~
In file included from /usr/include/c++/6/iostream:40:0,
                 from testlife.cpp:2:
/usr/include/c++/6/istream:803:5: note: candidate: template<class _Traits> std::basic_istream<char, _Traits>& std::operator>>(std::basic_istream<char, _Traits>&, unsigned char*)
     operator>>(basic_istream<char, _Traits>& __in, unsigned char* __s)
     ^~~~~~~~
/usr/include/c++/6/istream:803:5: note:   template argument deduction/substitution failed:
testlife.cpp:9:17: note:   cannot convert ‘std::endl’ (type ‘<unresolved overloaded function type>’) to type ‘unsigned char*’
   cin >> inp >> endl;
                 ^~~~
In file included from /usr/include/c++/6/iostream:40:0,
                 from testlife.cpp:2:
/usr/include/c++/6/istream:808:5: note: candidate: template<class _Traits> std::basic_istream<char, _Traits>& std::operator>>(std::basic_istream<char, _Traits>&, signed char*)
     operator>>(basic_istream<char, _Traits>& __in, signed char* __s)
     ^~~~~~~~
/usr/include/c++/6/istream:808:5: note:   template argument deduction/substitution failed:
testlife.cpp:9:17: note:   cannot convert ‘std::endl’ (type ‘<unresolved overloaded function type>’) to type ‘signed char*’
   cin >> inp >> endl;
                 ^~~~
In file included from /usr/include/c++/6/iostream:40:0,
                 from testlife.cpp:2:
/usr/include/c++/6/istream:924:5: note: candidate: template<class _CharT, class _Traits, class _Tp> std::basic_istream<_CharT, _Traits>& std::operator>>(std::basic_istream<_CharT, _Traits>&&, _Tp&)
     operator>>(basic_istream<_CharT, _Traits>&& __is, _Tp& __x)
     ^~~~~~~~
/usr/include/c++/6/istream:924:5: note:   template argument deduction/substitution failed:
testlife.cpp:9:17: note:   couldn't deduce template parameter ‘_Tp’
   cin >> inp >> endl;

鉴于我正在编写的简单代码块，我以前从未遇到过这样的错误，也无法调试它。我正在使用安装在 ubuntu 系统上的 g++ 编译器。

Answer 1

从 cin 中删除 endl陈述:

cin >> inp;

代替:

cin >> inp >> endl;