Go: package main

import "fmt"

func abs(x float64) float64 {
	if x < 0 {
		return -x
	}
	return x
}

func main() {
	var n int
	var x1, y1, x2, y2, x3, y3, x4, y4 float64
	fmt.Scan(&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)
		if abs((x2-x1)*(y4-y3) - (y2-y1)*(x4-x3)) < 1e-10 {
			fmt.Println("YES")
		} else {
			fmt.Println("NO")
		}
	}
}

Python: def parallelism(x1, y1, x2, y2, x3, y3, x4, y4):
    a1 = (y2-y1)/(x2-x1) if (x2-x1) != 0 else float("inf")
    a2 = (y4-y3)/(x4-x3) if (x4-x3) != 0 else float("inf")
    if a1 == a2:
        return "YES"
    else:
        return "NO"


if __name__ == "__main__":
    assert parallelism(0.0, 0.0, 1.0, 1.0, 1.0, 0.0, 2.0, 1.0) == "YES", "sample1"
    assert parallelism(3.0, 2.0, 9.0, 6.0, 13.0, 5.0, 7.0, 9.0) == "NO", "sample2"
    assert parallelism(3.0, 2.0, 9.0, 2.0, 13.0, 5.0, 7.0, 5.0) == "YES", "horizontal line"
    assert parallelism(3.0, 2.0, 3.0, 6.0, 13.0, 5.0, 13.0, 9.0) == "YES", "vertical line"

    n = int(input())
    for _ in range(n):
        x1, y1, x2, y2, x3, y3, x4, y4 = map(float, input().split())
        print(parallelism(x1, y1, x2, y2, x3, y3, x4, y4))

Python: n = int(input())
for i in range(n):
    x1, y1, x2, y2, x3, y3, x4, y4 = map(float, input().split())
    print('YES' if abs((x2 - x1)*(y4 - y3) - (x4 - x3)*(y2 - y1)) < 1e-10 else 'NO')

Python: from numpy import *
ABs=[]
CDs=[]
n = int(input())
for i in range(n):
    x_1, y_1, x_2, y_2, x_3, y_3, x_4, y_4, = map(float, input().split())
    AB = array([x_2 - x_1, y_2 - y_1])
    CD = array([x_4 - x_3, y_4 - y_3])
    ABs.append(AB)
    CDs.append(CD)
for i in range(n):
    if linalg.norm(cross(ABs[i],CDs[i]))==0.0:
        print("YES")
    else:
        print("NO")

Python: n = int(input())
for i in range(n):
    Date = list(map(float,input().split()))
    if Date[2] != Date[0] or Date[6] != Date[4]:
        if (Date[3] - Date[1]) * (Date[6] - Date[4]) == (Date[7] - Date[5]) * (Date[2] - Date[0]):
            print("YES")
            continue
        else:
            print("NO")
            continue
    elif Date[2] != Date[0] and Date[6] != Date[4]:
        print("YES")

Python: N = int(input())
for _ in range(0, N) :
  x1,y1,x2,y2,x3,y3,x4,y4 = list(map(float, input().split()))
  if ((y2 - y1) / (x2 - x1) == (y4 - y3) / (x4 - x3)) :
    print("YES")
  else :
    print("NO")

Python: num=int(input())
for i in range (num):
    info=list(map(float,input().split()))
    info=list(map(lambda x:int(x*10**6),info))
    if info[2]==info[0]:
        if info[6]==info[4]:
            print("YES")
        else:
            print("NO")
    elif info[6]==info[4]:
        if info[2]==info[0]:
            print("YES")
        else:
            print("NO")
    else:
        if (info[3]-info[1])/(info[2]-info[0])==(info[7]-info[5])/(info[6]-info[4]):
            print("YES")
        else:
            print("NO")

Python: n=int(input())
for j in range(n):
    p=[float(i) for i in input().split()]
    ab=(p[3]-p[1])/(p[2]-p[0])
    cd=(p[7]-p[5])/(p[6]-p[4])
    if ab==cd:
        print("YES")
    else:
        print("NO")

Python: n=int(input())
for _ in range(n):
    p=[float(i) for i in input().split()]
    if round((p[3]-p[1])/(p[2]-p[0]),5)==round((p[7]-p[5])/(p[6]-p[4]),5):
        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")
	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")