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;
}
然而，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;
我之前从未遇到过这样的错误，也没有根据我编写的简单代码块调试它。我正在使用ubuntu系统上安装的g ++编译器。
答案 0 :(得分：1)
从cin语句中删除endl：
cin >> inp;
而不是：
cin >> inp >> endl;
答案 1 :(得分：1)
std::istream的{{3}} I / O操纵器没有超载，因为错误消息明确说明了。
此外，您应该在接受输入时处理错误，否则您的循环将永远运行：
int main(){
while(true){
int inp;
if(cin >> inp && inp == 42) {
break;
}
else {
cin.clear();
cin.ignore(std::numeric_limits<std::streamsize>::max(), '\n');
continue;
}
cout << inp << endl;
}
return 0;
}