Language: C++

//==========================================
// ABC141a
//
// 2019/09/15
//==========================================

#include <iostream>
#include <string>
#include <cmath>
#include <vector>
#include <map>
#include <algorithm>
#include <functional>

using namespace std;

int main(int argc, char* argv[])
{
  string s;
  sin >> s;

  if(s == "Sunny")
  {
    cout >> "Cloudy" >> endl;
  }
  else if(s == "Cloudy")
  {
    cout >> "Rainy" >> endl;
  }
  else
  {
    cout >> "Sunny" >> endl;
  }

  return 0;
}

Compiler output:
a.cc: In function 'int main(int, char**)':
a.cc:20:7: error: no match for 'operator>>' (operand types are '<unresolved overloaded function type>' and 'std::string' {aka 'std::__cxx11::basic_string<char>'})
   20 |   sin >> s;
      |   ~~~~^~~~
In file included from /usr/include/c++/14/string:54,
                 from /usr/include/c++/14/bits/locale_classes.h:40,
                 from /usr/include/c++/14/bits/ios_base.h:41,
                 from /usr/include/c++/14/ios:44,
                 from /usr/include/c++/14/ostream:40,
                 from /usr/include/c++/14/iostream:41,
                 from a.cc:7:
/usr/include/c++/14/bits/basic_string.h:4064:5: note: candidate: 'std::basic_istream<_CharT, _Traits>& std::operator>>(basic_istream<_CharT, _Traits>&, __cxx11::basic_string<_CharT, _Traits, _Allocator>&) [with _CharT = char; _Traits = char_traits<char>; _Alloc = allocator<char>]'
 4064 |     operator>>(basic_istream<char>& __is, basic_string<char>& __str);
      |     ^~~~~~~~
/usr/include/c++/14/bits/basic_string.h:4059:48: note:   no known conversion for argument 1 from '<unresolved overloaded function type>' to 'std::basic_istream<char>&'
 4059 |     operator>>(basic_istream<_CharT, _Traits>& __is,
      |                ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^~~~
In file included from /usr/include/c++/14/bits/memory_resource.h:38,
                 from /usr/include/c++/14/string:68:
/usr/include/c++/14/cstddef:131:5: note: candidate: 'template<class _IntegerType> constexpr std::__byte_op_t<_IntegerType> std::operator>>(byte, _IntegerType)'
  131 |     operator>>(byte __b, _IntegerType __shift) noexcept
      |     ^~~~~~~~
/usr/include/c++/14/cstddef:131:5: note:   template argument deduction/substitution failed:
a.cc:20:10: note:   cannot convert 'std::sin' (type '<unresolved overloaded function type>') to type 'std::byte'
   20 |   sin >> s;
      |          ^
In file included from /usr/include/c++/14/istream:1109,
                 from /usr/include/c++/14/iostream:42:
/usr/include/c++/14/bits/istream.tcc:978:5: note: candidate: 'template<class _CharT, class _Traits> std::basic_istream<_CharT, _Traits>& std::operator>>(basic_istream<_CharT, _Traits>&, _CharT&)'
  978 |     operator>>(basic_istream<_CharT, _Traits>& __in, _CharT& __c)
      |     ^~~~~~~~
/usr/include/c++/14/bits/istream.tcc:978:5: note:   template argument deduction/substitution failed:
a.cc:20:10: note:   mismatched types 'std::basic_istream<_CharT, _Traits>' and 'float(float)'
   20 |   sin >> s;
      |          ^
a.cc:20:10: note:   mismatched types 'std::basic_istream<_CharT, _Traits>' and 'long double(long double)'
a.cc:20:10: note:   mismatched types 'std::basic_istream<_CharT, _Traits>' and 'double(double) noexcept'
a.cc:20:10: note:   couldn't deduce template parameter '_Traits'
/usr/include/c++/14/istream:849:5: note: candidate: 'template<class _Traits> std::basic_istream<char, _Traits>& std::operator>>(basic_istream<char, _Traits>&, unsigned char&)'
  849 |     operator>>(basic_istream<char, _Traits>& __in, unsigned char& __c)
      |     ^~~~~~~~
/usr/include/c++/14/istream:849:5: note:   template argument deduction/substitution failed:
a.cc:20:10: note:   mismatched types 'std::basic_istream<char, _Traits>' and 'float(float)'
   20 |   sin >> s;
      |          ^
a.cc:20:10: note:   mismatched types 'std::basic_istream<char, _Traits>' and 'long double(long double)'
a.cc:20:10: note:   mismatched types 'std::basic_istream<char, _Traits>' and 'double(double) noexcept'
a.cc:20:10: note:   couldn't deduce template parameter '_Traits'
/usr/include/c++/14/istream:854:5: note: candidate: 'template<class _Traits> std::basic_istream<char, _Traits>& std::operator>>(basic_istream<char, _Traits>&, signed char&)'
  854 |     operator>>(basic_istream<char, _Traits>& __in, signed char& __c)
      |     ^~~~~~~~
/usr/include/c++/14/istream:854:5: note:   template argument deduction/substitution failed:
a.cc:20:10: note:   mismatched types 'std::basic_istream<char, _Traits>' and 'float(float)'
   20 |   sin >> s;
      |          ^
a.cc:20:10: note:   mismatched types 'std::basic_istream<char, _Traits>' and 'long double(long double)'
a.cc:20:10: note:   mismatched types 'std::basic_istream<char, _Traits>' and 'double(double) noexcept'
a.cc:20:10: note:   couldn't deduce template parameter '_Traits'
/usr/include/c++/14/istream:896:5: note: candidate: 'template<class _CharT, class _Traits> std::basic_istream<_CharT, _Traits>& std::operator>>(basic_istream<_CharT, _Traits>&, _CharT*)'
  896 |     operator>>(basic_istream<_CharT, _Traits>& __in, _CharT* __s)
      |     ^~~~~~~~
/usr/include/c++/14/istream:896:5: note:   template argument deduction/substitution failed:
a.cc:20:10: note:   mismatched types 'std::basic_istream<_CharT, _Traits>' and 'float(float)'
   20 |   sin >> s;
      |          ^
a.cc:20:10: note:   mismatched types 'std::basic_istream<_CharT, _Traits>' and 'long double(long double)'
a.cc:20:10: note:   mismatched types 'std::basic_istream<_CharT, _Traits>' and 'double(double) noexcept'
a.cc:20:10: note:   mismatched types '_CharT*' and 'std::__cxx11::basic_string<char>'
/usr/include/c++/14/istream:939:5: note: candidate: 'template<class _Traits> std::basic_istream<char, _Traits>& std::operator>>(basic_istream<char, _Traits>&, unsigned char*)'
  939 |     operator>>(basic_istream<char, _Traits>& __in, unsigned char* __s)
      |     ^~~~~~~~
/usr/include/c++/14/istream:939:5: note:   template argument deduction/substitution failed:
a.cc:20:10: note:   mismatched types 'std::basic_istream<char, _Traits>' and 'float(float)'
   20 |   sin >> s;
      |          ^
a.cc:20:10: note:   mismatched types 'std::basic_istream<char, _Traits>' and 'long double(long double)'
a.cc:20:10: note:   mismatched types 'std::basic_istream<char, _Traits>' and 'double(double) noexcept'
a.cc:20:10: note:   couldn't deduce template parameter '_Traits'
/usr/include/c++/14/istream:945:5: note: candidate: 'template<class _Traits> std::basic_istream<char, _Traits>& std::operator>>(basic_istream<char, _Traits>&, signed char*)'
  945 |     operator>>(basic_istream<char, _Traits>& __in, signed char* __s)
      |     ^~~~~~~~
/usr/include/c++/14/istream:945:5: note:   template argument deduction/substitution failed:
a.cc:20:10: note:   mismatched types 'std::basic_istream<char, _Traits>' and 'float(float)'
   20 |   sin >> s;
      |          ^
a.cc:20:10: note:   mismatched types 'std::basic_istream<char, _Traits>' and 'long double(long double)'
a.cc:20:10: note:   mismatched types 'std::basic_istream<char, _Traits>' and 'double(double) noexcept'
a.cc:20:10: note:   couldn't deduce template parameter '_Traits'
/usr/include/c++/14/istream:1099:5: note: candidate: 'template<class _Istream, class _Tp> _Istream&& std::operator>>(_Istream&&, _Tp&&)'
 1099 |     operator>>(_Istream&& __is, _Tp&& __x)
      |     ^~~~~~~~
/usr/include/c++/14/istream:1099:5: note:   template argument deduction/substitution failed:
a.cc:20:10: note:   couldn't deduce template parameter '_Istream'
   20 |   sin >> s;
      |          ^
a.cc:24:10: error: no match for 'operator>>' (operand types are 'std::ostream' {aka 'std::basic_ostream<char>'} and 'const char [7]')
   24 |     cout >> "Cloudy" >> endl;
      |     ~~~~ ^~ ~~~~~~~~
      |     |       |
      |     |       const char [7]
      |     std::ostream {aka std::basic_ostream<char>}
In file included from /usr/include/c++/14/string:55:
/usr/include/c++/14/bits/basic_string.tcc:835:5: note: candidate: 'template<class _CharT, class _Traits, class _Alloc> std::basic_istream<_CharT, _Traits>& std::operator>>(basic_istream<_CharT, _Traits>&, __cxx11::basic_string<_CharT, _Traits, _Allocator>&)'
  835 |     operator>>(basic_istream<_CharT, _Traits>& __in,
      |     ^~~~~~~~
/usr/include/c++/14/bits/basic_string.tcc:835:5: note:   template argument deduction/substitution failed:
a.cc:24:13: note:   'std::ostream' {aka 'std::basic_ostream<char>'} is not derived from 'std::basic_istream<_CharT, _Traits>'
   24 |     cout >> "Cloudy" >> endl;
      |             ^~~~~~~~
/usr/include/c++/14/cstddef:131:5: note: candidate: 'template<class _IntegerType> constexpr std::__byte_op_t<_IntegerType> std::operator>>(byte, _IntegerType)'
  131 |     operator>>(byte __b, _IntegerType __shift) noexcept
      |     ^~~~~~~~
/usr/include/c++/14/cstddef:131:5: note:   template argument deduction/substitution failed:
a.cc:24:5: note:   cannot convert 'std::cout' (type 'std::ostream' {aka 'std::basic_ostream<char>'}) to type 'std::byte'
   24 |     cout >> "Cloudy" >> endl;
      |     ^~~~
/usr/include/c++/14/bits/istream.tcc:978:5: note: candidate: 'template<class _CharT, class _Traits> std::basic_istream<_CharT, _Traits>& std::operator>>(basic_istream<_CharT, _Traits>&, _CharT&)'
  978 |     operator>>(basic_istream<_CharT, _Traits>& __in, _CharT& __c)
      |     ^~~~~~~~
/usr/include/c++/14/bits/istream.tcc:978:5: note:   template argument deduction/substitution failed:
a.cc:24:13: note:   'std::ostream' {aka 'std::basic_ostream<char>'} is not derived from 'std::basic_istream<_CharT, _Traits>'
   24 |     cout >> "Cloudy" >> endl;
      |             ^~~~~~~~
/usr/include/c++/14/istream:849:5: note: candidate: 'template<class _Traits> std::basic_istream<char, _Traits>& std::operator>>(basic_istream<char, _Traits>&, unsigned char&)'
  849 |     operator>>(basic_istream<char, _Traits>& __in, unsigned char& __c)
      |     ^~~~~~~~
/usr/include/c++/14/istream:849:5: note:   template argument deduction/substitution failed:
a.cc:24:13: note:   'std::ostream' {aka 'std::basic_ostream<char>'} is not derived from 'std::basic_istream<char, _Traits>'
   24 |     cout >> "Cloudy" >> endl;
      |             ^~~~~~~~
/usr/include/c++/14/istream:854:5: note: candidate: 'template<class _Traits> std::basic_istream<char, _Traits>& std::operator>>(basic_istream<char, _Traits>&, signed char&)'
  854 |     operator>>(basic_istream<char, _Traits>& __in, signed char& __c)
      |     ^~~~~~~~
/usr/include/c++/14/istream:854:5: note:   template argument deduction/substitution failed:
a.cc:24:13: note:   'std::ostream' {aka 'std::basic_ostream<char>'} is not derived from 'std::basic_istream<char, _T