Go: package main

import (
	"bufio"
	"os"
	"strconv"
	"fmt"
	"strings"
)

var scanner = bufio.NewScanner(os.Stdin)

func nextInt() int {
	scanner.Scan()
	i, e := strconv.Atoi(scanner.Text())
	if e != nil {
		panic(e)
	}
	return i
}

func main() {
	n := nextInt()
	for i := 0; i < n; i++ {
		scanner.Scan()
		points := strings.Split(scanner.Text(), " ")
		fpoints := make([]float64, 0)
		for _, v := range points {
			tmp, _ := strconv.ParseFloat(v, 64)
			fpoints = append(fpoints, tmp)
		}
		a := (fpoints[1]-fpoints[3])/(fpoints[0]-fpoints[2])
		b := (fpoints[5]-fpoints[7])/(fpoints[4]-fpoints[6])
		if a == b {
			fmt.Println("YES")
		} else {
			fmt.Println("NO")
		}
	}
}

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

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

C++: #include <iostream>
using namespace std;
int main() {
  int n;
  double x1, y1, x2, y2, x3, y3, x4, y4, a, b, c, d;
  cin >> n;
  while (n--) {
    cin >> x1 >> y1 >> x2 >> y2 >> x3 >> y3 >> x4 >> y4;
    a = x2 - x1, b = x4 - x3, c = y2 - y1, d = y4 - y3;
    if ((a == 0 && b == 0 && c != 0 && d != 0) || c / a == d / b) {
      cout << "YES" << endl;
    } else {
      cout << "NO" << endl;
    }
  }
  return 0;
}

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

int main()
{
	int n, i, j;
	float x[4], y[4];

	cin >> n;

	for (i = 0; i < n; i++)
	{
		for (j = 0; j < 4; j++)
			cin >> x[j] >> y[j];

		if (((x[1]-x[0])/(y[1]-y[0])) == ((x[3]-x[2])/(y[3]-y[2])))
			cout << "YES" << endl;
		else
			cout << "NO" << endl;
	}
	return 0;
}

C++: #include <iostream>
using namespace std;
int main(){
	int n , i , j ;
	double
	 x1, x2 , x3 , x4 , y1 , y2 , y3 , y4 ;
	while( cin >> n ){
		double ab , cd ;
		for( i=1 ; i<=n ; i++ ){
			cin >> x1 >> y1 >> x2 >> y2 >> x3 >> y3 >> x4 >> y4 ;
			ab = ( y2 - y1 ) / ( x2 - x1 );
		cd = ( y4 - y3 ) / ( x4 - x3 );
		if( ab==cd )
			cout <<"YES" << endl;
		else 
			cout << "NO" << endl;
	}
}
}

C++: #include<string>
#include<vector>
#include<iostream>
#include<algorithm>
#include<cstdio>
#include<cstdlib>
#include<sstream>
#include<functional>
#include<map>
#include<stack>
#include<set>
#include<cmath>

#define REP(i,s,e) for(int i=int(s);i<=int(e);i++)
#define rep(i,n) for(int i=0;i<int(n);i++)

#define EPS 1e-6

using namespace std;

int main(){

	int n;
	double x1,y1,x2,y2,x3,y3,x4,y4;

	cin >> n;

	rep(i,n){

	cin >> x1 >> y1 >> x2 >> y2 >> x3 >> y3 >> x4 >> y4;

	double a=y2-y1; double b=x2-x1;
	double d=y4-y3; double e=x4-x3;

	if(a*e-d*b==0) cout << "YES" << endl;
	else cout << "NO" << endl;

	}

	return 0;
}

C++: #include<iostream>
#include<cmath>
#define EPS 0.000000000001
using namespace std;

int main(){
	int n;
	double x[4], y[4];
	cin >> n;
	while (n--){
		for (int i = 0; i < 4; i++)
			cin >> x[i] >> y[i];
		if (abs((x[1] - x[0]) * (y[3] - y[2]) - (x[3] - x[2]) * (y[1] - y[0])) < EPS)
			cout << "YES" << endl;
		else if (abs(x[0] - x[1] < EPS && x[2] - x[3]) < EPS)
			cout << "YES" << endl;
		else if (abs(y[0] - y[1] < EPS && y[2] - y[3]) < EPS)
			cout << "YES" << endl;
		else
			cout << "NO" << endl;
	}
	return 0;
}

C++: #include <stdio.h>
 
int main() {
    double x1, x2, x3, x4, y1, y2, y3, y4;
    int n;
 
    int i;
 
 
    scanf("%d", &n);
 
    for(i = 0; i < n; i++) {
        scanf("%lf %lf %lf %lf %lf %lf %lf %lf", &x1, &y1, &x2, &y2, &x3, &y3, &x4, &y4);
 
        if((x2 - x1) * (y4 - y3) - (y2 - y1) * (x4 - x3))
            printf("NO\n");
        else
            printf("YES\n");
    }
 
    return 0;
}

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

using namespace std;

#define EPS 1e-5

int main(){
  double a,b,c,d,e,f,g,h;
  int t;

  cin >> t;
  while(t--){
    cin >> a >> b >> c >> d >> e >> f >> g >> h;
    
    c -= a,d -= b,g -= e,h -= f;
    
    cout << (fabs(c*g-d*h) > EPS ? "NO" : "YES") << endl;
  }
  
  return 0;
}

C++: #include <cassert>
#include <cmath>
#include <iostream>
#include <vector>

struct Point
{
    double x;
    double y;
};
struct Line
{
    Line(const Point& a, const Point& b)
    : p1(a), p2(b) {}
    Point p1;
    Point p2;
};
double GetSlope(const Line& line)
{
    return
    (line.p2.y - line.p1.y) /
    (line.p2.x - line.p1.x);
}
bool IsParallel(const Line& l1, const Line&l2)
{
    // std::cerr << GetSlope(l1) << std::endl;
    // std::cerr << GetSlope(l2) << std::endl;
    return std::fabs(GetSlope(l1) - GetSlope(l2)) < 0.00001;
}
bool IsParallel(const std::vector<Point>& points)
{
    assert(points.size() == 4);
    return IsParallel(Line(points[0], points[1]), Line(points[2], points[3]));
}
std::vector<Point> Input(std::istream& is)
{
    std::vector<Point> points(4);
    for(int i = 0; i < points.size(); ++i){
        is >> points[i].x >> points[i].y;
    }
    return points;
}
int main()
{
    int n;
    std::cin >> n;
    for(int i = 0; i < n; ++i) {
        std::vector<Point> points = Input(std::cin);
        std::cout << (IsParallel(points) ? "YES" : "NO") << std::endl; 
    }
    return 0;
}

C++: #include "bits/stdc++.h"
#include<unordered_map>
#include<unordered_set>
#pragma warning(disable:4996)
using namespace std;
using ld =long double;
const ld eps = 1e-9;

enum R_Way {
	R_Left,
	R_Front,
	R_Right,
	R_Back,

	R_Dummy,
};

struct Dice {
	int tp;
	int bo;
	int no;
	int so;
	int ea;
	int we;
	Dice(int tp_, int bo_, int no_, int so_, int ea_, int we_) :
		tp(tp_), bo(bo_), no(no_), so(so_), ea(ea_), we(we_) {

	}
	Dice(vector<int>pips_) {

	}

	Dice() {
		tp = 1;
		/*bo = 6;
		no = 2;
		so = 5;
		ea = 3;
		we = 4;*/
	}

	int rotate(const R_Way way) {
		switch (way) {
		case R_Right: {
			int c = tp;
			tp = we;
			we = bo;
			bo = ea;
			ea = c;
		}
					  break;
		case R_Back: {
			int c = tp;
			tp = so;
			so = bo;
			bo = no;
			no = c;
		}
					 break;
		case R_Left: {
			int c = tp;
			tp = ea;
			ea = bo;
			bo = we;
			we = c;
		}
					 break;
		case R_Front: {
			int c = tp;
			tp = no;
			no = bo;
			bo = so;
			so = c;
		}
					  break;
		default:
			assert(false);
		}
		return tp;
	}
	int rotate(const int way) {
		return rotate(static_cast<R_Way>(way));
	}
	void spin(const int  clockwise) {
		if (!clockwise) {

			rotate(R_Way::R_Left);
			rotate(R_Way::R_Back);
			rotate(R_Way::R_Right);
		}
		else {

			rotate(R_Way::R_Left);
			rotate(R_Way::R_Front);
			rotate(R_Way::R_Right);
		}
	}
	int hash()const {
		return tp + we * 6 + no * 36;
	}
};
int geteast(int top, int south) {
	map<pair<int, int>, int>mp;
	mp[make_pair(1, 2)] = 3;
	mp[make_pair(1, 3)] = 5;
	mp[make_pair(2, 3)] = 1;
	mp[make_pair(2, 4)] = 6;
	bool rev = false;
	if (top >= 4) {
		rev = !rev; top = 7 - top;
	}
	if (south >= 4) {
		rev = !rev; south = 7 - south;
	}
	if (top > south) {
		rev = !rev; swap(top, south);
	}
	return mp[make_pair(top, south)];
}

bool connect(char a, char b) {
	return abs(a-b)==abs('A'-'a');
}

bool solve(bitset<8>&used, const int now, vector<Dice>&dices) {
	if(now==8)return true;
	else {
		for (int i = 0; i < 8; ++i) {
			if(used[i])continue;
			else {
				for (int tp = 1; tp <= 6; ++tp) {
					for (int so = 1; so <= 6; ++so) {
						if(tp==so||tp+so==7)continue;
						int le=geteast(tp,so);

						vector<int>perms(6);
						perms[0]=tp-1;
						//perms[1]=
					}
				}
			}
		}
	}
}

int main()
{
	int N;cin>>N;
	for (int i = 0; i < N; ++i) {
		vector<ld>v(8);
		for(int j=0;j<8;++j)cin>>v[j];

		ld ax=v[2]-v[0];
		ld ay=v[3]-v[1];

		ld bx=v[6]-v[4];
		ld by=v[7]-v[5];

		bool ok=abs(ax*by-bx*ay)<eps/1000;

		if(ok)cout<<"YES"<<endl;
		else cout<<"NO"<<endl;
	}
	return 0;
}