Go: package main

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

func check(x, y, x1, y1, x2, y2 float64) float64 {
	return (x2-x1)*y - (y2-y1)*x + x1*y2 - x2*y1
}

func main() {
	scanner := bufio.NewScanner(os.Stdin)
	a := make([]float64, 8)
	for scanner.Scan() {
		info := strings.Split(scanner.Text(), ",")
		for j := 0; j < 8; j++ {
			a[j], _ = strconv.ParseFloat(info[j], 64)
		}
		if check(a[0], a[1], a[2],a[3], a[6], a[7])*check(a[4], a[5], a[2], a[3], a[6], a[7]) < 0 && check(a[6], a[7], a[0], a[1], a[4], a[5])*check(a[2],a[3], a[0], a[1], a[4], a[5]) < 0 {
			fmt.Println("YES")	
		} else {
			fmt.Println("NO")
		}
	}
}

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

using namespace std;

typedef complex<double> P;

//XYÀW
#define X real()
#define Y imag()

double tri2s(double xa, double ya, double xb, double yb, double xc, double yc){
     double a, b, c, s;
    
     a = sqrt((xb - xc) * (xb - xc) + (yb - yc) * (yb - yc));
     b = sqrt((xa - xc) * (xa - xc) + (ya - yc) * (ya - yc));
     c = sqrt((xb - xa) * (xb - xa) + (yb - ya) * (yb - ya));
    
     s = (a+b+c) / 2;

	 cout << sqrt(s * (s - a) * (s - b) * (s - c)) << endl;
    
     return sqrt(s * (s - a) * (s - b) * (s - c));
}

double p2deg(double xa, double ya, double xb, double yb, double xc, double yc){
  double a, b, c, s, cos;
    
     a = sqrt((xb - xc) * (xb - xc) + (yb - yc) * (yb - yc));
     b = sqrt((xa - xc) * (xa - xc) + (ya - yc) * (ya - yc));
     c = sqrt((xb - xa) * (xb - xa) + (yb - ya) * (yb - ya));

	 cos = (b * b + c * c - a * a) / 2 * b * c;

	 return acos(cos);

}

// ¼üp1,p2Æüªp3,p4Ìð·»è
// (n < 0)<=>ð· , (n == 0)<=>¼üã, (n > 0)<=>ð·µÄ¢È¢  
double isIntersect(P p1, P p2, P p3, P p4){  
    return ( (p1.X-p2.X)*(p3.Y-p1.Y) + (p1.Y-p2.Y)*(p1.X-p3.X)) * ((p1.X-p2.X)*(p4.Y-p1.Y) + (p1.Y-p2.Y)*(p1.X-p4.X));  
}

int main(void){
     double x[4], y[4];
     double sq;
     double tri[4];
     bool isok = true;
    
     while(cin >> x[0]){
          cin.ignore(); cin >> y[0];
          cin.ignore(); cin >> x[1]; cin.ignore(); cin >> y[1];
          cin.ignore(); cin >> x[2]; cin.ignore(); cin >> y[2];
          cin.ignore(); cin >> x[3]; cin.ignore(); cin >> y[3];
		  
		  P a(x[0], y[0]);
		  P b(x[1], y[1]);
		  P c(x[2], y[2]);
		  P d(x[3], y[3]);
		  /*
          sq = tri2s(x[0], y[0], x[1], y[1], x[2], y[2]) + tri2s(x[0],y[0],x[2],y[2],x[3],y[3]);
         
          tri[0] = tri2s(x[0], y[0], x[1], y[1], x[2], y[2]);
          tri[1] = tri2s(x[0], y[0], x[1], y[1], x[3], y[3]);
          tri[2] = tri2s(x[0], y[0], x[2], y[2], x[3], y[3]);
          tri[3] = tri2s(x[1], y[1], x[2], y[3], x[3], y[3]);
         
          for(int i=0;i<4;i++){
               if(tri[i] > sq) isok = false;
          }
          if(tri2s(x[0],y[0],x[1],y[1],x[2],y[2]) + tri2s(x[0],y[0],x[2],y[2],x[3],y[3]) ==
			 tri2s(x[0],y[0],x[1],y[1],x[3],y[3]) + tri2s(x[2],y[2],x[1],y[1],x[3],y[3]) ){
               cout << "YES" << endl;
          }else{
               cout << "NO" << endl;
          }
          isok = true;
		  */
		  
		  if( isIntersect(a,c,b,d) > 0.0 || isIntersect(b,d,a,c) > 0.0 ){
			cout << "NO" << endl;
		  }else{
			cout << "YES" << endl;
		  }
	 }
	 return 0;
}

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

int main(){
	double xa,ya,xb,yb,xc,yc,xd,yd;
	double sab,sac,sbc,tab,tac,tbc;
	bool flag;
	
	while(scanf("%lf,%lf,%lf,%lf,%lf,%lf,%lf,%lf",
	&xa,&ya,&xb,&yb,&xc,&yc,&xd,&yd)!=EOF)
	{
		sab=(yb-ya)/(xb-xa);
		sac=(yc-ya)/(xc-xa);
		sbc=(yc-yb)/(xc-xb);
		
		tab=ya-sab*xa;
		tac=ya-sac*xa;
		tbc=yb-sbc*xb;
		
		flag=(sab*xd+tab-yd>0&&sac*xd+tac-yd<0&&sbc*xd+tbc-yd<0);
		
		cout<<(flag?"YES\n":"NO\n");
	}
	return 0;
}

C++: #include <bits/stdc++.h>
using namespace std;
#define FOR(i, s, n) for(int i = s; i < (int)n; i++)
#define per(i, n) for(int i = n; i >= 0; i--)
#define ROF(i, s, n) for(int i = s; i >= (int)n; i--)
#define FORIT(i, A) for (auto i : A)
#define PRINT(x) cout << (x) << "\n"
#define ALL(a) (a).begin(),(a).end()
#define RALL(a) (a).rbegin(), (a).rend()
#define MP make_pair
#define EACH(i, n) for (__typeof((n).begin()) i = (n).begin(); i != (n).end(); ++i)
#define SZ(a) int((a).size())
#define EXIST(s,e) ((s).find(e)!=(s).end())
#define SORT(c) sort((c).begin(),(c).end())
#define CLR(a) memset((a), 0 ,sizeof(a))
#define NCLR(a) memset((a), -1 ,sizeof(a))
#define dump(x) cout << #x << " = " << (x) << "\n";
#define debug(x) cout << #x << " = " << (x) << " (L" << __LINE__ << ")" << " " << __FILE__ << "\n";
#define sq(n) (n) * (n)
typedef vector<int> VI;
typedef vector<VI> VVI;
typedef vector<string> VS;
typedef pair<int, int> PII;
typedef long long LL;
typedef vector<LL> VLL;
typedef vector<VLL> VVLL;
typedef unsigned int uint;
typedef unsigned long long ull;
typedef priority_queue<int> maxpq;
typedef priority_queue< int, vector<int>, greater<int> > minpq;
typedef complex<double> P;
static const double EPS = 1e-10;
static const double PI = acos( -1.0 );
static const int mod = 1000000007;
static const int INF = 1 << 30;
static const LL LL_INF = 1152921504606846976;
static const int dx[] = { -1, 0, 1, 0, 1, -1, 1, -1 };
static const int dy[] = { 0, -1, 0, 1, 1, 1, -1, -1 };

bool collision_detection( double x1, double y1, double x2, double y2, double x3, double y3, double xp, double yp ) {
	x2 -= x1;
	x3 -= x1;
	xp -= x1;
	y2 -= y1;
	y3 -= y1;
	yp -= y1;
	double t_size = fabs( ( x2 * y3 - y2 * x3 ) / 2 );
	t_size -= fabs( ( x2 * yp -  y2 * xp ) / 2 );
	t_size -= fabs( ( x3 * yp -  y3 * xp ) / 2 );
	x2 -= xp;
	x3 -= xp;
	y2 -= yp;
	y3 -= yp;
	yp = xp = 0;
	t_size -= fabs( ( x2 * y3 - y2 * x3 ) / 2 );
	return fabs( t_size ) < 1e-10;
}

int main() {
	double x[ 4 ], y[ 4 ];
	while ( ~scanf( "%lf,%lf,%lf,%lf,%lf,%lf,%lf,%lf", &x[ 0 ], &y[ 0 ], &x[ 1 ], &y[ 1 ], &x[ 2 ], &y[ 2 ], &x[ 3 ], &y[ 3 ] ) ) {
		bool print_yes = true;
		for ( int i = 0; i < 4; i++ ) {
			if ( collision_detection( x[ ( i + 1 ) % 4 ], y[ ( i + 1 ) % 4 ], x[ ( i + 2 ) % 4 ], y[ ( i + 2 ) % 4 ], x[ ( i + 3 ) % 4 ], y[ ( i + 3 ) % 4 ], x[ i ], y[ i ] ) ) {
				print_yes = false;
				break;
			}
		}
		printf( "%s\n", print_yes ? "YES" : "NO" );
	}
	return 0;
}

C++: #include <iostream>
#include <algorithm>
#include <map>
#include <vector>
#include <string>
#include <cstdio>
#include <cmath>

using namespace std;
double x[4], y[4];
double ab, bc, cd, da, ac, bd;

double len(double x1, double y1, double x2, double y2)
{
    return sqrt(pow(x1-x2, 2) + pow(y1-y2, 2));
}

// Heron's Formula
double square(double a, double b, double c)
{
    double s = (a + b + c) / 2.0;
    return sqrt(s * (s-a) * (s-b) * (s-c));
}


int main(void)
{
    while(~scanf("%lf,%lf,%lf,%lf,%lf,%lf,%lf,%lf",x,y,x+1,y+1,x+2,y+2,x+3,y+3)) {
        ab = len(x[0],y[0],x[1],y[1]);
        bc = len(x[1],y[1],x[2],y[2]);
        cd = len(x[2],y[2],x[3],y[3]);
        da = len(x[3],y[3],x[1],y[1]);
        ac = len(x[0],y[0],x[2],y[2]);
        bd = len(x[4],y[4],x[1],y[1]);
        double s1,s2,s3,s4;
        s1 = square(ab, bd, da);
        s2 = square(cd, bd, bc);
        s3 = square(ac, cd, da);
        s4 = square(ab, bc, ac);
        double comp1;
        comp1 = (s1+s2) - (s3+s4);

        if(fabs(comp1) <= 0.01)
            puts("YES");
        else
            puts("NO");
    }
    return 0;
}