Go: package main

import (
        "fmt"
        "math/big"
)

func main() {
        var x1, x2, x3, x4, y1, y2, y3, y4 big.Float
        var n int
        fmt.Scanf("%d", &n)
        for i := 0; i < n; i++ {
                fmt.Scanf("%f %f %f %f %f %f %f %f",
                        &x1, &y1, &x2, &y2, &x3, &y3, &x4, &y4)
                var lx, ly, mx, my, mul1, mul2, sub, zz big.Float
                lx.Sub(&x2, &x1)
                ly.Sub(&y2, &y1)
                mx.Sub(&x4, &x3)
                my.Sub(&y4, &y3)
                mul1.Mul(&lx, &my)
                mul2.Mul(&ly, &mx)
                sub.Sub(&mul1, &mul2)
                zz.SetFloat64(0.0)

                if sub.Cmp(&zz) == 0 {
                        fmt.Println("YES")
                } else {
                        fmt.Println("NO")
                }
        }
}

C++: //#define _GRIBCXX_DEBUG
#include <algorithm>
#include <cctype>
#include <climits>
#include <cmath>
#include <complex>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <ctime>
#include <deque>
#include <functional>
#include <iostream>
#include <iomanip>
#include <list>
#include <map>
#include <memory>
#include <numeric>
#include <queue>
#include <set>
#include <stack>
#include <string>
#include <utility>
#include <vector>
using namespace std;


// ?????¬???????????¬??????
#pragma region MACRO
#define P(x) cout << (x) << endl
#define p(x) cout << (x)
#define PED cout << "\n"
#define rep(i,n) for(int i=0; i<(int)n; ++i)
#define REP(i,x,n) for(int i=x; i<(int)n; ++i)
#define repi(i,n) for(int i=0; i<=(int)n; ++i)
#define REPI(i,x,n) for(int i=x; i<=(int)n; ++i)
#define ILP while(true)
#define FOR(i,c) for(__typeof((c).begin())!=(c).begin(); i!=(c).end(); ++i)
#define ALL(c) (c).begin(), (c).end()
#define mp make_pair
#pragma endregion

// ???
#pragma region TYPE_DEF
typedef long long ll;
typedef pair<int, int> pii;
typedef pair<string, string> pss;
typedef pair<string, int> psi;
typedef pair<int, string> pis;
typedef vector<int> vi;
typedef vector<double> vd;
typedef vector<long> vl;
typedef vector<long long> vll;
typedef vector<string> vs;
#pragma endregion

// Effective std
#pragma region ESTD
template<typename C, typename T>
constexpr int count(C& c, T t) { return count(ALL(c), t); }
template<typename C, typename F>
constexpr int count_if(C& c, F f) { return count_if(ALL(c), f); }
template<typename C, typename T>
void erase(C& c, T t) { remove(ALL(c), t), c.end(); }
template<typename C>
void remove(vector<C>& c, unsigned int index) { c.erase(c.begin()+index); }
template<typename C, typename T, typename U>
constexpr void replace(C& c, T t, U u) { replace(ALL(c), t, u); }
template<typename C, typename F, typename U>
constexpr void replace_if(C& c, F f, U u) { (ALL(c), f, u); }
template<typename C>
constexpr void reverse(C& c) { reverse(ALL(c)); }
template<typename C>
constexpr void sort(C& c) { sort(ALL(c)); }
template<typename C, typename Pred>
constexpr void sort(C& c, Pred p) { sort(ALL(c), p); }
#pragma endregion

// ?????°
#pragma region CONST_VAL
#define PI (2*acos(0.0))
#define EPS (1e-9)
#define MOD (int)(1e9+7)
#pragma endregion

bool func(vector<long double> x, vector<long double> y) {
    if ((y[1] - y[0]) * (x[3] - x[2]) == (y[3] - y[2]) * (x[1] - x[0])) return true;
    return false;
}

int main()
{
    int n;
    cin >> n;
    vector<long double> x(4);
    vector<long double> y(4);

    while(n--) {
        rep(i,4) cin >> x[i] >> y[i];
        P(func(x,y) ? "YES" : "NO");
    }
    return 0;
}

C++: #include <complex>
#include <iostream>
#include <cmath>
using namespace std;

typedef complex<double> xy_t;
double cross_product(xy_t a, xy_t b) { return (conj(a)*b).imag(); }
const double eps = 1e-11;
double x[4],y[4];
int N;
int main() {
	cin >> N;
	for (int i=0; i<N; ++i) {
		for (int i=0; i<4; ++i) {
			cin >> x[i] >> y[i];
			x[i] *= 1e5;
			y[i] *= 1e5;
		}
		xy_t a[2] = {
					xy_t(x[0],y[0]) - xy_t(x[1],y[1]),
					xy_t(x[2],y[2]) - xy_t(x[3],y[3])
				};
		bool p = cross_product(a[0],a[1]) == 0;
		cout << ( p ? "Yes" : "No") << endl;
	}
}

C++: #include<cstdio>
#include<cmath>

int main(){
	int n;
	double x[4], y[4];
	int xi[4], yi[4];
	scanf("%d", &n);
	for(int i = 0; i < n; i++){
		scanf("%lf %lf %lf %lf %lf %lf %lf %lf", &x[0],&y[0],&x[1],&y[1],&x[2],&y[2],&x[3],&y[3]);

		for(int i = 0; i < 4; i++){
			xi[i] = (int)(x[i] * 1000000);
			yi[i] = (int)(y[i] * 1000000);
		}
		
		if((yi[0] - yi[1])*(xi[2] - xi[3]) == (xi[0] - xi[1])*(yi[2] - yi[3])){
			printf("YES\n");
		}else{
			printf("NO\n");
		}
	}
	return 0;
}

C++: #include<iostream>
#include<complex>
#include<cmath>
#include<string>
#include<queue>
using namespace std;
typedef complex<double> xy_t;
int main()
{
  int n;
  double x[4],y[4];
  queue<string> qs;
  cin >> n;
  for( int i = 0; i < n; ++i){
    xy_t p[4];
    for( int j = 0; j < 4; ++j){
      cin >> x[j] >> y[j];
      p[j] = xy_t(x[j],y[j]);
    }
    double S;
    S =(conj(p[0] - p[1])*(p[2] - p[3])).imag();
    if( S == 0) qs.push("YES");
    else qs.push("NO");
  }
  while(!qs.empty()){
    cout << qs.front() << endl;
    qs.pop();
  }
}

C++: #include <iostream>

int main(){
	double x1 , y1 , x2 , y2 , x3 , y3 , x4 , y4;
	int n;
	std::cin >> n;
	for(int i=0 ; i<n ; ++i){
		std::cin >> x1 >> y1 >> x2 >> y2 >> x3 >> y3 >> x4 >> y4;
		bool parallel=false;
		if(x1==x2 && x3==x4) {
			parallel=true;
			goto result;
		}
		else if(x1==x2 || x3==x4) {
			goto result;
		}
		else if ((y2-y1)/(x2-x1)==(y4-y3)/(x4-x3)) {
			parallel=true;
		}
		result:
		std::cout << ( parallel ? "YES" : "NO") << std::endl;
	}
	return 0; 
}

C++: #include <iostream>
using namespace std;

typedef struct {
  double x;
  double y;
} point;

int main() {
  point a, b, c, d;
  int n;
  cin >> n;
  while (n--) {
    cin >> a.x >> a.y >> b.x >> b.y >> c.x >> c.y >> d.x >> d.y;
    point p, q;
    p.x = b.x - a.x;
    p.y = b.y - a.y;
    q.x = d.x - c.x;
    q.y = d.y - c.y;

    if (-1e-10  < p.x * q.y - p.y * q.x && p.x * q.y - p.y * q.x < 1e-10)
      cout << "YES" << endl;
    else
      cout << "NO" << endl;
  }
  return 0;
}

C++: #include <bits/stdc++.h>
#define rep(i,l,n) for(int i=l;i<n;i++)
using namespace std;

int main(){
	int n;
	cin>>n;
	rep(i,0,n){
		double x1,y1,x2,y2,x3,y3,x4,y4;
        cin>>x1>>y1>>x2>>y2>>x3>>y3>>x4>>y4;
        double a1,a2;
        a1=(y2-y1)/(x2-x1);
        a2=(y4-y3)/(x4-x3);
        if(a1==a2)
        {
            cout<<"YES"<<endl;
        }
        else{
            cout<<"NO"<<endl;
        }
	}
}

C++: #define _USE_MATH_DEFINES
#include<iostream>
#include<iomanip>
#include<algorithm>
#include<cctype>
#include<cmath>
#include<cstdio>
#include<deque>
#include<list>
#include<set>
#include<stack>
#include<string>
#include<sstream>
#include<map>
#include<queue>
#include<vector>
using namespace std;

int main() {
	int n;
	cin >> n;
	for (int i = 0; i < n; i++) {
		double x1, y1, x2, y2, x3, y3, x4, y4;
		cin >> x1 >> y1 >> x2 >> y2 >> x3 >> y3 >> x4 >> y4;
		double ABx = x2 - x1,
			ABy = y2 - y1,
			CDx = x4 - x3,
			CDy = y4 - y3;
		if (ABx / ABy == CDx / CDy)cout << "YES" << endl;
		else cout << "NO" << endl;
	}
	return 0;
}

C++: #include<iostream>
using namespace std;int main(){
int n=2,ab=0,cd=0;
double point1[20]={0.0,0.0,1.0,1.0,1.0,0.0,2.0,1.0};
double point2[20]={3.0,2.0,9.0,6.0,13.0,5.0,7.0,9.0};

ab = ((1.0-0.0)/(1.0-0.0));
cd = ((1.0-0.0)/(2.0-1.0)); if( ab = cd) cout << "YES\n" ;
else cout << "NO\n" ;

ab = ((6.0-2.0)/(9.0-3.0));
cd = ((9.0-5.0)/(7.0-13.0)); if( ab = cd) cout << "YES\n" ;
else cout << "NO\n" ;    return 0;
}