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++: v#include<iostream>
#include<string>
#include<cstdio>
#include<algorithm>
#include<stack>
#include<queue>
#include<vector>
#include<cmath>
#include<utility>
#include<set>
#include<complex>
#include<map>
#define vi vector<int>
#define vvi vector<vector<int> >
#define ll long long int
#define vl vector<ll>
#define vvl vector<vector<ll>>
#define vb vector<bool>
#define vc vector<char>
#define vs vector<string>
#define ld long double
#define INF 1e9
#define EPS 0.0000000001
#define rep(i,n) for(int i=0;i<n;i++)
#define loop(i,s,n) for(int i=s;i<n;i++)
#define CC puts("-------ok--------");
#define all(in) in.begin(), in.end()
using namespace std;
typedef pair<int, int> pii;
#define MAX 99999999
int main(){
    typedef pair<double, double>pdd;
    vector<pdd>v(5);
    int n;cin>>n;
    rep(i,n){
        rep(i,4)cin>>v[i].first>>v[i].second;
        if(v[0].first<v[1].first)swap(v[0],v[1]);
        if(v[2].first<v[3].first)swap(v[2],v[3]);
        double d1=(v[0].second-v[1].second)/(v[0].first-v[1].first);
        double d2=(v[2].second-v[3].second)/(v[2].first-v[3].first);
        if(d1==d2&&(v[0].first-v[1].first!=0))cout<<"YES"<<endl;
        else cout<<"NO"<<endl;
    }
}

C++: #include <iostream>

using namespace std;

int main()
{
	int n;
	double x[4], y[4], vx[2], vy[2], kx, ky;

	cin >> n;

	for (int i=0; i<n; i++)
	{
		cin >> x[0] >> y[0] >> x[1] >> y[1] >> x[2] >> y[2] >> x[3] >> y[3];

		vx[0] = x[1]-x[0];
		vx[1] = x[3]-x[2];
		vy[0] = y[1]-y[0];
		vy[1] = y[3]-y[2];

		kx = vx[0]/vx[1];
		ky = vy[0]/vy[1];

		if(kx == ky) {
			cout << "YES" << endl;
		}
		else {
			cout << "NO"  << endl;
		}
	}

	return 0;
}

C++: #include <bits/stdc++.h>

using namespace std;

int main() {
  int n; 
  cin >> n;

  double cx[4], cy[4];
  for (int i = 0 ; i < n; ++i) {
    for (int j = 0; j < 4; j++)
      cin >> cx[j] >> cy[j];
  
    double kx = (cy[1] - cy[0]) / (cx[1] - cx[0]);
    double ky = (cy[3] - cy[2]) / (cx[3] - cx[2]);
    
    if (abs(kx - ky) < 0.0001) {
      cout << "YES" << endl;
    } else {
      cout << "NO" << endl;
    }
  }
}

C++: int main(){
	int n,i,j;
	double x[4],y[4];
	scanf("%d",&n);
	for(i=0;i<n;i++){
		for(j=0;j<4;j++)scanf("%d %d",&x[j],&y[j]);
		if(((y[0]-y[1])/(x[0]-x[1]))==((y[2]-y[3])/(x[2]-x[3])))printf("YES\n");
		else printf("NO\n");
	}
}

C++: #include <stdio.h>
#include <iostream>
#include <vector>
#include <string>
#include <math.h>
#include <algorithm>
using namespace std;
#define INF 0x7FFFFFFF

int main(){
  int n;
  cin>>n;
  while(n){
    n--;
    vector<double> x(4,0);
    vector<double> y(4,0);
    for(int i=0;i<4;i++){
      cin>>x[i]>>y[i];
    }
    double xa,xb,ya,yb;
    xa=x[1]-x[0];
    xb=x[3]-x[2];
    ya=y[1]-y[0];
    yb=y[3]-y[2];
    double a;
    a=xa*yb-xb*ya;
    if(-0.000005<=a&&a<0.000005){
      cout<<"YES"<<endl;
    }
    else{
      cout<<"NO"<<endl;
    }
  }
}

C++: #include <bits/stdc++.h>
using namespace std;

typedef double Real;
typedef complex<Real> Point;
typedef pair<Point,Point> Line;

const Real EPS=1e-5;


inline Point vec(const Line& a){
    return a.second-a.first;
}

Real dot(Point a,Point b){
    return (conj(a)*b).real();
}

Real cross(Point a,Point b){
    return (conj(a)*b).imag();
}

inline int sgn(Real a,Real b=0){
    return a < b - EPS ? -1 : a > b + EPS ? 1 : 0;
}

inline bool near(Point a,Point b){
    return !sgn(abs(a-b));
}

inline bool is_orthogonal(Line la,Line lb){
    return !sgn(dot(vec(la),vec(lb)));
}

inline bool is_parallel(Line la,Line lb){
    return !sgn(cross(vec(la),vec(lb)));
}

inline bool is_intersected_line(Line la,Line lb){
    return !is_parallel(la,lb);
}

inline Real arg(const Point& base,const Point& a,const Point& b){
    return arg((b-base)/(a-base));
}

inline Real sr(Real a){
    return sqrt(max(a,(Real)0));
}

inline Real dist(Point a,Point b){
    return abs(a-b);
}

inline Real length(Point a){
    return abs(a);
}

inline Point unit_vector(Point a){
    return a / abs(a);
}


Point rotate(Point x,Real rad){
    return Point(x.real()*cos(rad)-x.imag()*sin(rad),x.real()*sin(rad)+x.imag()*cos(rad));
}                             



int main(){
    cin.tie(0);
    ios::sync_with_stdio(false);

    int n;
    Point A[4];

    cin>>n;
    for(int i=0;i<n;i++){
        for(auto &t:A){
            double x,y;
            cin>>x>>y;
            t=Point(x,y);
        }

        Line la=make_pair(A[0],A[1]),lb=make_pair(A[2],A[3]);

        cout << (is_parallel(la,lb) ? "YES" : "NO") << endl;
    }

    return 0;
}

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

const double EPS = 1e-10;

double add(double a, double b) {
	if (abs(a + b) < EPS * (abs(a) + abs(b)))
		return 0;
	return a + b;
}

struct P {
	double x, y;
	P() {};
	P(double x, double y) : x(x), y(y) {
	}

	P operator + (P p) {
		return P(add(x, p.x), add(y, p.y));
	}

	P operator - (P p) {
		return P(add(x, -p.x), add(y, -p.y));
	}

	P operator * (double d) {
		return P(x * d, y * d);
	}

	P operator / (double d) {
		return P(x / d, y / d);
	}

	// 内積
	double dot(P p) {
		return add(x * p.x, y * p.y);
	}

	// 外積
	double det(P p) {
		return add(x * p.y, -y * p.x);
	}
};

// 線分上に点があるか
bool on_seg(P p1, P p2, P q) {
	return (p1 - q).det(p2 - q) == 0 && (p1 - q).dot(p2 - q) <= 0;
}

// 直線と直線の交点
P intersection(P p1, P p2, P q1, P q2) {
	return p1 + (p2 - p1) * ((q2 - q1).det(q1 - p1) / (q2 - q1).det(p2 - p1));
}

// 2直線の直行判定
bool line_orth(P a1, P a2, P b1, P b2) {
	return fabs((a1 - a2).dot(b1 - b2)) < EPS;
}

// 2直線の垂直判定
bool line_paral(P a1, P a2, P b1, P b2) {
	return fabs((a1 - a2).det(b1 - b2)) < EPS;
}

int main(void) {
	int N;
	P p[4];
	cin >> N;
	for (int i = 0; i < N; i++) {
		for (int j = 0; j < 4; j++) {
			cin >> p[j].x >> p[j].y;
		}cout << (line_paral(p[0], p[1], p[2], p[3]) ? "YES" : "NO") << endl;
	}
}