为啥出现 error C2109:subscipt requires array or pointer type

for (int i=0;i<100;i++)
    {p[0].x=a[i].x;
    p[0].y=a[i].y-r[i];   
p[1].x=(int)(a[i].x+r[i]*cos(18*PI/180));
p[1].y=(int)(a[i].y-r[i]*sin(18*PI/180));   
p[2].x=(int)(a[i].x+r[i]*cos(54*PI/180));   
p[2].y=(int)(a[i].y+r[i]*sin(54*PI/180));   
p[3].x=(int)(a[i].x-r[i]*cos(54*PI/180));   
p[3].y=(int)(a[i].y+r[i]*sin(54*PI/180));   
p[4].x=(int)(a[i].x-r[i]*cos(18*PI/180));   
p[4].y=(int)(a[i].y-r[i]*sin(18*PI/180));
p[5].x=a[i].x;   
p[5].y=a[i].y-r[i];   
pDC->SelectObject(&pen1);
pDC->MoveTo(p[0].x,p[0].y);   
pDC->LineTo(p[2].x,p[2].y);   
pDC->LineTo(p[4].x,p[4].y);   
pDC->LineTo(p[1].x,p[1].y);
pDC->LineTo(p[3].x,p[3].y);   
pDC->LineTo(p[5].x,p[5].y);}