Language: C++

#include <iostream>
#include <complex>
using namespace std;
typedef complex<double> P;
const double EPS = 1e-9;
int main(){
	int N;
	cin >> N;
	while(N--){
		P a,b,c,d;
		cin >> a.real() >> a.imag() >> b.real() >> b.imag() >> c.real() >> c.imag() >> d.real() >> d.imag();
		P one = a-b;
		P two = c-d;
		bool f = false;
		if( abs(one.imag()) < EPS || abs(two.imag()) < EPS ){
			f = abs(one.imag()) < EPS && abs(two.imag()) < EPS;
		}else{
			f = abs(one.real()/one.imag() - two.real()/two.imag()) < EPS;
		}
		cout << (f?"YES":"NO") << endl;
	}
// }

Compiler output:
a.cc: In function 'int main()':
a.cc:11:21: error: no match for 'operator>>' (operand types are 'std::istream' {aka 'std::basic_istream<char>'} and 'double')
   11 |                 cin >> a.real() >> a.imag() >> b.real() >> b.imag() >> c.real() >> c.imag() >> d.real() >> d.imag();
      |                 ~~~ ^~ ~~~~~~~~
      |                 |            |
      |                 |            double
      |                 std::istream {aka std::basic_istream<char>}
In file included from /usr/include/c++/14/iostream:42,
                 from a.cc:1:
/usr/include/c++/14/istream:170:7: note: candidate: 'std::basic_istream<_CharT, _Traits>::__istream_type& std::basic_istream<_CharT, _Traits>::operator>>(bool&) [with _CharT = char; _Traits = std::char_traits<char>; __istream_type = std::basic_istream<char>]' (near match)
  170 |       operator>>(bool& __n)
      |       ^~~~~~~~
/usr/include/c++/14/istream:170:7: note:   conversion of argument 1 would be ill-formed:
a.cc:11:30: error: cannot bind non-const lvalue reference of type 'bool&' to a value of type 'double'
   11 |                 cin >> a.real() >> a.imag() >> b.real() >> b.imag() >> c.real() >> c.imag() >> d.real() >> d.imag();
      |                        ~~~~~~^~
/usr/include/c++/14/istream:174:7: note: candidate: 'std::basic_istream<_CharT, _Traits>& std::basic_istream<_CharT, _Traits>::operator>>(short int&) [with _CharT = char; _Traits = std::char_traits<char>]' (near match)
  174 |       operator>>(short& __n);
      |       ^~~~~~~~
/usr/include/c++/14/istream:174:7: note:   conversion of argument 1 would be ill-formed:
a.cc:11:30: error: cannot bind non-const lvalue reference of type 'short int&' to a value of type 'double'
   11 |                 cin >> a.real() >> a.imag() >> b.real() >> b.imag() >> c.real() >> c.imag() >> d.real() >> d.imag();
      |                        ~~~~~~^~
/usr/include/c++/14/istream:177:7: 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>; __istream_type = std::basic_istream<char>]' (near match)
  177 |       operator>>(unsigned short& __n)
      |       ^~~~~~~~
/usr/include/c++/14/istream:177:7: note:   conversion of argument 1 would be ill-formed:
a.cc:11:30: error: cannot bind non-const lvalue reference of type 'short unsigned int&' to a value of type 'double'
   11 |                 cin >> a.real() >> a.imag() >> b.real() >> b.imag() >> c.real() >> c.imag() >> d.real() >> d.imag();
      |                        ~~~~~~^~
/usr/include/c++/14/istream:181:7: note: candidate: 'std::basic_istream<_CharT, _Traits>& std::basic_istream<_CharT, _Traits>::operator>>(int&) [with _CharT = char; _Traits = std::char_traits<char>]' (near match)
  181 |       operator>>(int& __n);
      |       ^~~~~~~~
/usr/include/c++/14/istream:181:7: note:   conversion of argument 1 would be ill-formed:
a.cc:11:30: error: cannot bind non-const lvalue reference of type 'int&' to a value of type 'double'
   11 |                 cin >> a.real() >> a.imag() >> b.real() >> b.imag() >> c.real() >> c.imag() >> d.real() >> d.imag();
      |                        ~~~~~~^~
/usr/include/c++/14/istream:184:7: 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>; __istream_type = std::basic_istream<char>]' (near match)
  184 |       operator>>(unsigned int& __n)
      |       ^~~~~~~~
/usr/include/c++/14/istream:184:7: note:   conversion of argument 1 would be ill-formed:
a.cc:11:30: error: cannot bind non-const lvalue reference of type 'unsigned int&' to a value of type 'double'
   11 |                 cin >> a.real() >> a.imag() >> b.real() >> b.imag() >> c.real() >> c.imag() >> d.real() >> d.imag();
      |                        ~~~~~~^~
/usr/include/c++/14/istream:188:7: 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>; __istream_type = std::basic_istream<char>]' (near match)
  188 |       operator>>(long& __n)
      |       ^~~~~~~~
/usr/include/c++/14/istream:188:7: note:   conversion of argument 1 would be ill-formed:
a.cc:11:30: error: cannot bind non-const lvalue reference of type 'long int&' to a value of type 'double'
   11 |                 cin >> a.real() >> a.imag() >> b.real() >> b.imag() >> c.real() >> c.imag() >> d.real() >> d.imag();
      |                        ~~~~~~^~
/usr/include/c++/14/istream:192:7: 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>; __istream_type = std::basic_istream<char>]' (near match)
  192 |       operator>>(unsigned long& __n)
      |       ^~~~~~~~
/usr/include/c++/14/istream:192:7: note:   conversion of argument 1 would be ill-formed:
a.cc:11:30: error: cannot bind non-const lvalue reference of type 'long unsigned int&' to a value of type 'double'
   11 |                 cin >> a.real() >> a.imag() >> b.real() >> b.imag() >> c.real() >> c.imag() >> d.real() >> d.imag();
      |                        ~~~~~~^~
/usr/include/c++/14/istream:199:7: 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>; __istream_type = std::basic_istream<char>]' (near match)
  199 |       operator>>(long long& __n)
      |       ^~~~~~~~
/usr/include/c++/14/istream:199:7: note:   conversion of argument 1 would be ill-formed:
a.cc:11:30: error: cannot bind non-const lvalue reference of type 'long long int&' to a value of type 'double'
   11 |                 cin >> a.real() >> a.imag() >> b.real() >> b.imag() >> c.real() >> c.imag() >> d.real() >> d.imag();
      |                        ~~~~~~^~
/usr/include/c++/14/istream:203:7: 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>; __istream_type = std::basic_istream<char>]' (near match)
  203 |       operator>>(unsigned long long& __n)
      |       ^~~~~~~~
/usr/include/c++/14/istream:203:7: note:   conversion of argument 1 would be ill-formed:
a.cc:11:30: error: cannot bind non-const lvalue reference of type 'long long unsigned int&' to a value of type 'double'
   11 |                 cin >> a.real() >> a.imag() >> b.real() >> b.imag() >> c.real() >> c.imag() >> d.real() >> d.imag();
      |                        ~~~~~~^~
/usr/include/c++/14/istream:219:7: note: candidate: 'std::basic_istream<_CharT, _Traits>::__istream_type& std::basic_istream<_CharT, _Traits>::operator>>(float&) [with _CharT = char; _Traits = std::char_traits<char>; __istream_type = std::basic_istream<char>]' (near match)
  219 |       operator>>(float& __f)
      |       ^~~~~~~~
/usr/include/c++/14/istream:219:7: note:   conversion of argument 1 would be ill-formed:
a.cc:11:30: error: cannot bind non-const lvalue reference of type 'float&' to a value of type 'double'
   11 |                 cin >> a.real() >> a.imag() >> b.real() >> b.imag() >> c.real() >> c.imag() >> d.real() >> d.imag();
      |                        ~~~~~~^~
/usr/include/c++/14/istream:223:7: note: candidate: 'std::basic_istream<_CharT, _Traits>::__istream_type& std::basic_istream<_CharT, _Traits>::operator>>(double&) [with _CharT = char; _Traits = std::char_traits<char>; __istream_type = std::basic_istream<char>]' (near match)
  223 |       operator>>(double& __f)
      |       ^~~~~~~~
/usr/include/c++/14/istream:223:7: note:   conversion of argument 1 would be ill-formed:
a.cc:11:30: error: cannot bind non-const lvalue reference of type 'double&' to an rvalue of type 'double'
   11 |                 cin >> a.real() >> a.imag() >> b.real() >> b.imag() >> c.real() >> c.imag() >> d.real() >> d.imag();
      |                        ~~~~~~^~
/usr/include/c++/14/istream:227:7: 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>; __istream_type = std::basic_istream<char>]' (near match)
  227 |       operator>>(long double& __f)
      |       ^~~~~~~~
/usr/include/c++/14/istream:227:7: note:   conversion of argument 1 would be ill-formed:
a.cc:11:30: error: cannot bind non-const lvalue reference of type 'long double&' to a value of type 'double'
   11 |                 cin >> a.real() >> a.imag() >> b.real() >> b.imag() >> c.real() >> c.imag() >> d.real() >> d.imag();
      |                        ~~~~~~^~
/usr/include/c++/14/istream:328:7: note: candidate: 'std::basic_istream<_CharT, _Traits>::__istream_type& std::basic_istream<_CharT, _Traits>::operator>>(void*&) [with _CharT = char; _Traits = std::char_traits<char>; __istream_type = std::basic_istream<char>]'
  328 |       operator>>(void*& __p)
      |       ^~~~~~~~
/usr/include/c++/14/istream:328:25: note:   no known conversion for argument 1 from 'double' to 'void*&'
  328 |       operator>>(void*& __p)
      |                  ~~~~~~~^~~
/usr/include/c++/14/istream:122:7: note: candidate: 'std::basic_istream<_CharT, _Traits>::__istream_type& std::basic_istream<_CharT, _Traits>::operator>>(__istream_type& (*)(__istream_type&)) [with _CharT = char; _Traits = std::char_traits<char>; __istream_type = std::basic_istream<char>]'
  122 |       operator>>(__istream_type& (*__pf)(__istream_type&))
      |       ^~~~~~~~
/usr/include/c++/14/istream:122:36: note:   no known conversion for argument 1 from 'double' to 'std::basic_istream<char>::__istream_type& (*)(std::basic_istream<char>::__istream_type&)' {aka 'std::basic_istream<char>& (*)(std::basic_istream<char>&)'}
  122 |       operator>>(__istream_type& (*__pf)(__istream_type&))
      |                  ~~~~~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~
/usr/include/c++/14/istream:126:7: note: candidate: 'std::b