(搬运工)判断点是否在线段或直线上

var p:Point = new Point( 10 , 15 );
var p1:Point = new Point( 10 , 10 );
var p2:Point = new Point( 10 , 20 );

trace (isPointOnSegment(p,p1,p2));

function isPointOnSegment(p:Point,p1:Point,p2:Point): Boolean
{
//差积是否为0，判断是否在同一直线上
//trace(( p1.x -p.x )*( p2.y-p.y) -( p2.x -p.x )*( p1.y-p.y));
if (( p1.x -p.x )*( p2.y-p.y) -( p2.x -p.x )*( p1.y-p.y)!= 0 )
{
trace ( "11111111111111" );
return false ;
}
//判断是否在线段上
if ((p.x > p1.x && p.x > p2.x) || (p.x < p1.x && p.x < p2.x))
{
trace ( "22222222222" );
return false ;
}
if ((p.y > p1.y && p.y > p2.y) || (p.y < p1.y && p.y < p2.y))
{
trace ( "3333333333333" );
return false ;
}
return true ;
}