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")
		}
	}
}

Python: n=int(input())
for i in range(n):
    a=[float(i) for i in input().split()]
    dx1=a[2]-a[0]
    dy1=a[3]-a[1]
    dx2=a[6]-a[4]
    dy2=a[7]-a[5]
    if dx1==0 or dx2==0:
        if dx1==0 and dx2==0:
            print("YES")
        else:
            print("NO")
    elif dy1/dx1==dy2/dx2:
        print("YES")
    else:
        print("NO")

Python: n = int(input())
for i in range(n):
  x1, y1, x2, y2, x3, y3, x4, y4 = [float(j) for j in input().split()]
  if x2 == x1:
    if x4 == x3:
      print("YES")
    else:
      print("NO")
  elif x4 == x3:
    print("NO")
  else:
    print("YES" if (y2 - y1) / (x2 - x1) == (y4 - y3) / (x4 - x3) else "NO")

Python: class Point(object):
    def __init__(self, x, y):
        self.x = x
        self.y = y
    def __str__(self):
        return "x = {0}, y = {1}".format(self.x, self.y)

class Line(Point):
    eps = 0.000001
    def __init__(self, p1, p2):
        self.p1 = p1
        self.p2 = p2

    def isParallel(self, another_p):
        try:
            angle1 = (self.p1.y - self.p2.y) / (self.p1.x - self.p2.x)
            angle2 = (another_p.p1.y - another_p.p2.y) / (another_p.p1.x - another_p.p2.x)
            if angle1 >= angle2-self.eps and angle1 <= angle2+self.eps:
                return True
            else:
                return False
        except ZeroDivisionError:
            if self.p1.x == self.p2.x and another_p.p1.x == another_p.p2.x:
                return True
            else:
                return False


n = int(input())
for i in range(n):
    x1, y1, x2, y2, x3, y3, x4, y4 = map(float, input().split())
    A = Point(x1, y1)
    B = Point(x2, y2)
    C = Point(x3, y3)
    D = Point(x4, y4)

    AB = Line(A, B)
    CD = Line(C, D)

    if AB.isParallel(CD):
        print("YES")
    else:
        print("NO")

Python: # AOJ 0021: Parallelism
# Python3 2018.6.15 bal4u

n = int(input())
for i in range(n):
	ax1, ay1, ax2, ay2, bx1, by1, bx2, by2 = list(map(float, input().split()))
	if abs((ay2-ay1)*(bx2-bx1)-(by2-by1)*(ax2-ax1)) < 1e-8: print('YES')
	else: print('NO')

Python: n = int(input())
for i in range(n):
	line = list(map(float,input().split()))
	if round(line[2] - line[0], 7) == 0:
		if round(line[6] - line[4], 7) == 0:
			print("YES")
		else:
			print("NO")
	elif round(line[6] - line[4], 7) == 0:
		pass
	else:
		AB = (line[3] - line[1]) / (line[2] - line[0])
		CD = (line[7] - line[5]) / (line[6] - line[4])
		if round(AB - CD, 8) == 0:
			print("YES")
		else:
			print("NO")

Python: import sys
cases = int(input())
i = 0
while i < cases:
   for line in sys.stdin.readlines():
       x1 , y1 , x2 , y2 , x3 , y3 , x4 , y4 = map(float,line.split())
       m1 = (y2 - y1)/(x2 - x1)
       m2 = (y4 - y3)/(x4 - x3)
       if(m1 == m2):
           print("YES")
       else:
           print("NO")
   i += 1

Python: n = int(input())
for i in range(n):
    x1, y1, x2, y2, x3, y3, x4, y4 = map(float, input().split())
    if x1 == x2 and x3 == x4:
        print("YES")
    elif x1 == x2 or x3 == x4:
        print("NO")
    elif (y2 - y1) / (x2 - x1) == (y4 - y3) / (x4 - x3):
        print("YES")
    else:
        print("NO")

Python: n = int(input())
for i in range(n):
	line = list(map(float,input().split()))
	AB = (line[3] - line[1]) / (line[2] - line[0])
	CD = (line[7] - line[5]) / (line[6] - line[4])
	if round(AB - CD,8) == 0:
		print("YES")
	else:
		print("NO")

Python: import sys
f = sys.stdin

def cross(a, b):
    return a.real * b.imag - a.imag * b.real
 
n = f.readline()
for line in f:
    a, b, c, d = [x + y * 1j for x, y in zip(* [map(float, line.split())] * 2)]
    print('YES' if cross(a - b, c - d) == 0.0 else 'NO')

Python: n = int(input())
for i in range(n):
	line = list(map(float,input().split()))
	if round(line[2] - line[0], 5) == 0:
		if round(line[6] - line[4], 5) == 0:
			print("YES")
		else:
			print("NO")
	elif round(line[6] - line[4], 5) == 0:
		pass
	else:
		AB = (line[3] - line[1]) / (line[2] - line[0])
		CD = (line[7] - line[5]) / (line[6] - line[4])
		if round(AB - CD, 11) == 0:
			print("YES")
		else:
			print("NO")

Python: n = int(raw_input)
for i in range(n):
  p = map( float, raw_input().split() )
  flag = ( p[ 1 ] - p[ 0 ] ) * ( p[ 7 ] - p[ 6 ] ) == ( p[ 3 ] - p[ 2 ] ) * ( p[ 5 ] - p[ 4 ] )
  print ( flag and 'YES' ) or 'NO'

Python: EPS = 1e-10
for q in range(int(input())):
    l = list(map(float, input().split()))
    if abs((l[3] - l[1]) * (l[6] - l[4]) - (l[7] - l[5]) * (l[2] - l[0])) < EPS:
        print('YES')
    else:
        print('NO')

Python: import sys

# args = sys.argv

args = [int(float(a)) for line in sys.stdin]


class Point():
  def __init__(self,x,y):
      self.x = x
      self.y = y

  def __sub__(self,oth):
    self.x = self.x - oth.x
    self.y = self.y - oth.y
    return Point(self.x,self.y)

  def __str__(self):
    return "%s(%r)" %(self.__class__,self.__dict__)

for _ in range(args[0]):
  if _ == 0:
    pass
  else:
    A,B,C,D = ([Point(i,i+1) for i in range(0,8,2)])
    tmp = B - A
    tmp2 = C - D
    tmp3 = (tmp.x * tmp2.y) - (tmp.y * tmp2.x)
    if int(tmp3) == 0:
      print("YES")
    else:
      print("NO")

Python: N = eval(input())
for _ in range(N):
	x1, y1, x2, y2, x3, y3, x4, y4 = [eval(item) for item in input().split()]
	if abs(x1 - x2) < 1e-10 or abs(x3 - x4) < 1e-10:
		print('YES' if abs(x1 - x2) < 1e-10 and abs(x3 - x4) < 1e-10 else 'NO')
	elif abs((y1 - y2)/(x1 - x2) - (y3 - y4)/(x3 - x4)) < 1e-10:
		print('YES')
	else:
		print('NO')

Python: n = int(input())
for _ in range(n):
    x1, y1, x2, y2, x3, y3, x4, y4 = map(float, input().split())
    dx12, dx34, dy12, dy34 = x1 - x2, x3 - x4, y1 - y2, y3 - y4
    if not ((dx12 or dy12) and (dx34 or dy34)):
        print('NO')
    else:
        print('YES' if dx12 * dy34 == dy12 * dx34 else 'NO')

Python: while True:
    try:
        a=[float(i) for i in input().split()]
    except:
        break
    dx1=a[2]-a[0]
    dy1=a[3]-a[1]
    dx2=a[6]-a[4]
    dy2=a[7]-a[5]
    if dx1==0 or dx2==0:
        if dx1==0 and dx2==0:
            print("YES")
        else:
            print("NO")
    elif dy1/dx1==dy2/dx2:
        print("YES")
    else:
        print("NO")

Python: n = int(input())
for i in range(n):
	line = list(map(float,input().split()))
	if round(line[2] - line[0], 2) == 0:
		if round(line[6] - line[4], 2) == 0:
			print("YES")
		else:
			print("NO")
	elif round(line[6] - line[4], 2) == 0:
		pass
	else:
		AB = (line[3] - line[1]) / (line[2] - line[0])
		CD = (line[7] - line[5]) / (line[6] - line[4])
		if round(AB - CD, 8) == 0:
			print("YES")
		else:
			print("NO")

Python: import math
def naiseki(x1,y1,x2,y2,x3,y3,x4,y4):
    if ((x2-x1)*(y4-y3)-(y2-y1)*(x4-x3)) == 0:
        print("YES")
    else:
        print("NO")
a = int(input())
f=[]
for i in range(a):
    f.append(map(float,raw_input().split()))
for g in f:
    try:
        x1=g[0]
        y1=g[1]
        x2=g[2]
        y2=g[3]
        x3=g[4]
        y3=g[5]
        x4=g[6]
        y4=g[7]
        naiseki(x1,y1,x2,y2,x3,y3,x4,y4)
    except:
        print("NO")