/* 判断待求点在哪个圆心范围内 */
int yanxin(double cx, double cy)
{
struct point u1;
struct point u2;
struct point v1;
struct point v2;
double A = 0.0;
int i = 0;
int loop = 0;
cx = (R_L > 0) ? cx : cx * R_L; /* 判断应用在左幅还是右幅 */
do{
u1.x = SD_start_x[i];
u1.y = SD_start_y[i];
u2.x = SD_end_x[i];
u2.y = SD_end_y[i];
v1.x = SD_circle_x[i]+sd_d;
v1.y = SD_circle_y[i]+sd_h;
sd_scr = FS_D(v1.x, v1.y, cx, cy);
A = FS_A(v1.x, v1.y, cx, cy,0);
/* 把线延长2.929米（暂定），再做判断 */
v2.x = cx + (2.929 + sd_scr) * (cos(A*PI/180.0));
v2.y = cy + (2.929 + sd_scr) * (sin(A*PI/180.0));
loop = (intersect_in(u1,u2,v1,v2));
if (loop) break ;
i += 1;
if (i >= SD_size) return FALSE; /* 超出下限终止 */
}while(!loop);
if (SD_R[i] == 0) return FALSE;
if (SD_R[i] > 0) sd_cqw = sd_scr - (SD_R[i]+sd_r);
if (SD_R[i] < 0) sd_cqw = fabs(cx-v1.x) - abs((SD_R[i]+sd_r));
return TRUE;
}
bool crossline(int x1,int x2,int y1,int y2)
{
point u1,u2,v1,v2;
u1.x=a[x1][0];u1.y=a[x1][1];
u2.x=a[x2][0];u2.y=a[x2][1];
v1.x=a[y1][0];v1.y=a[y1][1];
v2.x=a[y2][0];v2.y=a[y2][1];
return intersect_in(u1,u2,v1,v2);
}
double solve()
{
if(l1.a.y==l1.b.y || l2.a.y==l2.b.y || (!intersect_in(l1,l2)) ||
parallel(l1,l2))
return 0;
if(l1.a.y>l1.b.y+eps) swap(l1.a,l1.b);
if(l2.a.y>l2.b.y+eps) swap(l2.a,l2.b);
point ip=intersection(l1,l2);
if(l1.b.y<ip.y || l2.b.y+eps<ip.y)
return 0;
point h,l;
bool flag=true;
if(l1.b.y>l2.b.y+eps)
{
h=l1.b;
l=l2.b;
}
else if(l1.b.y<l2.b.y-eps)
{
h=l2.b;
l=l1.b;
}
else
{
flag=false;
h=l2.b;
l=l1.b;
}
if(flag && ((h.x>=l.x && ip.x+eps< l.x &&(l.y-ip.y)*(h.x-ip.x) < (l.x-ip.x)*(h.y-ip.y)+eps) ||
(h.x<=l.x && ip.x> l.x+eps&&(l.y-ip.y)*(h.x-ip.x) > (l.x-ip.x)*(h.y-ip.y)-eps)))
return 0;
line tmp;
tmp.a.x=min(min(l1.a.x,l2.a.x),min(l1.b.x,l2.b.x));
tmp.b.x=max(max(l1.a.x,l2.a.x),max(l1.b.x,l2.b.x));
tmp.a.y=tmp.b.y=l.y;
point p1=intersection(tmp,l1);
point p2=intersection(tmp,l2);
double dist=p1.x-p2.x;
if(dist<-eps) dist*=-1;
return dist*(l.y-ip.y)/2;
}
