vectors and line point distance

#include <iostream>
#include <cmath>


using namespace std;


typedef struct
{
    double x, y;
}pp;


double absl(pp p)
{
    //double r;
    return p.x-p.y;
}
pp to_vec(pp p, pp q)
{
    pp r;
    r.x = q.x-p.x;
    r.y = q.y-p.y;
    return r;
}
//Compute the dot product AB . BC
/*int dot(int[] A, int[] B, int[] C){
        AB = new int[2];
        BC = new int[2];
        AB[0] = B[0]-A[0];
        AB[1] = B[1]-A[1];
        BC[0] = C[0]-B[0];
        BC[1] = C[1]-B[1];
        int dot = AB[0] * BC[0] + AB[1] * BC[1];
        return dot;
}*/
double dot(pp p, pp q)
{
    double r;
    r = p.x*q.x + p.y*q.y;
    return r;
}
    //Compute the cross product AB X AC
/*int cross(int[] A, int[] B, int[] C){
        AB = new int[2];
        AC = new int[2];
        AB[0] = B[0]-A[0];
        AB[1] = B[1]-A[1];
        AC[0] = C[0]-A[0];
        AC[1] = C[1]-A[1];
        int cross = AB[0] * AC[1] - AB[1] * AC[0];
        return cross;
}*/
pp crs(pp p, pp q)
{
    pp r;
    r.x = p.x*q.y;
    r.y = p.y*q.x;
    //x1*y2 - y1*x2
    return r;
}
    //Compute the distance from A to B
/*double distance(int[] A, int[] B){
        int d1 = A[0] - B[0];
        int d2 = A[1] - B[1];
        return sqrt(d1*d1+d2*d2);
}*/
double dis(pp p, pp q)
{
    double r;
    r = sqrt((p.x-q.x)*(p.x-q.x)+(p.y-q.y)*(p.y-q.y));
    return r;
}
    //Compute the distance from AB to C
    //if isSegment is true, AB is a segment, not a line.
/*double linePointDist(int[] A, int[] B, int[] C, boolean isSegment){
        double dist = cross(A,B,C) / distance(A,B);
        if(isSegment){
            int dot1 = dot(A,B,C);
            if(dot1 > 0)return distance(B,C);
            int dot2 = dot(B,A,C);
            if(dot2 > 0)return distance(A,C);
        }
        return abs(dist);
}*/
double dist(pp p, pp q, pp r, bool isSegment)
{
    double s;
    s = absl(crs(to_vec(p, q), to_vec(p, r))) / dis(p, q);
    if(isSegment)
    {
        int dot1 = dot(to_vec(p, q), to_vec(p, r));
        if(dot1 > 0)    return dis(q,r);
        int dot2 = dot(to_vec(q, p), to_vec(q, r));
        if(dot2 > 0)    return dis(p,r);
    }
    return fabs(s);
}


int main()
{
    pp A, B, C;
    while(1)
    {
        printf("Enter 3 points:\n");
        scanf("%lf %lf %lf %lf %lf %lf", &A.x, &A.y, &B.x, &B.y, &C.x, &C.y);


        pp AB, BC;
        AB = to_vec(A, B);  //make vector
        printf("AB i-> %lf j-> %lf\n", AB.x, AB.y);
        BC = to_vec(B, C);  //make vector
        printf("BC i-> %lf j-> %lf\n", BC.x, BC.y);


        double dt;
        pp cr;
        dt = dot(AB, BC);   //AB . BC
        printf("AB . BC %lf\n", dt);
        cr = crs(AB, BC);   //AB X BC
        printf("AB X BC i-> %lf j-> %lf\n", cr.x, cr.y);


        double d;
        d = dis(A, B);  //distance from A to B
        printf("distance from A to B is %lf\n", d);


        bool issegment;
        double p_d1, p_d2;
        issegment = 0;
        p_d1 = dist(A, B, C, issegment);    //distance from AB to C (AB is a line)
        printf("distance from AB line  to C is %lf\n", p_d1);
        issegment = 1;
        p_d2 = dist(A, B, C, issegment);    //distance from AB to C (AB is a segment)
        printf("distance from AB segment to C is %lf\n", p_d2);
    }
    return 0;
}