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)
		}
		if fpoints[0] == fpoints[2] && fpoints[4] == fpoints[6] {
			fmt.Println("YES")
			continue
		}
		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++: #define _CRT_SECURE_NO_WARNINGS
#include <iostream>
#include <cstdio>
#include <cstring>
#include <ctime>
#include <string>
#include <vector>
#include <algorithm>
#include <cmath>
#include <sstream>
#include <utility>
using namespace std;
typedef long long ll;
typedef vector<int> vi;
typedef vector<vi> vvi;
typedef pair<int,int> pii;
#define all(c) (c).begin(), (c).end()
#define loop(i,a,b) for(ll i=a; i<ll(b); i++)
#define rep(i,b) loop(i,0,b)
#define each(e,c) for(auto&e:c)
#define pb push_back
#define eb emplace_back
#define mp make_pair
#define mt make_tuple
#define lb lower_bound
#define ub upper_bound
#ifdef DEBUG
#define dump(...) (cerr<<#__VA_ARGS__<<" = "<<(DUMP(),__VA_ARGS__).str()<<" ["<<__LINE__<<"]"<<endl)
struct DUMP:ostringstream{template<class T>DUMP &operator,(const T&t){if(this->tellp())*this<<", ";*this<<t;return *this;}};
#else
#define dump(...)
#endif
 
int main(){
    int n; cin>>n;
    rep(_,n){
        ll x[2][2], y[2][2];
        rep(i,2){
            rep(j,2){
                double x_,y_;
                cin >> x_ >> y_;
                x[i][j] = x_*100000;
                y[i][j] = y_*100000;
            }
        }
        ll dx1=x[0][0]-x[0][1], dy1=y[0][0]-y[0][1];
        ll dx2=x[1][0]-x[1][1], dy2=y[1][0]-y[1][1];
        dump(dx1,dx2,dy1,dy2);
        puts(dx1*dy2==dx2*dy1 ? "YES" : "NO");
    }
}

C++: #include <iostream>
#include <vector>
#include <algorithm>
#include <map>
#include <cmath>
#include <complex>
using namespace std;
#define rep(i,n) for (int i=0; i < (n); i++)

typedef double D;
typedef complex<D> P;
typedef pair<P, P> L;
typedef vector<P> VP;
const D EPS = 1e-9;
#define X real()
#define Y imag()
#define LE(n,m) ((n) < (m) + EPS)
#define GE(n,m) ((n) + EPS > (m))
#define EQ(n,m) (abs((n)-(m)) < EPS)

D dot(P a, P b) {
  return (conj(a)*b).X;
}

D cross(P a, P b) {
  return (conj(a)*b).Y;
}

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;
    P a, b, c, d;
    a = P(x1, y1);
    b = P(x2, y2);
    c = P(x3, y3);
    d = P(x4, y4);
    if (EQ(cross(a-b, c-d), 0)) {
      std::cout << "YES" << std::endl;
    }else {
      std::cout << "NO" << std::endl;
    }
  }

}