我有一些代表和方法:
delegate Point Translate(Point p);
delegate Translate Transform(Translate t);
Translate forward = p => new Point(p.X + 1, p.Y);
问题:我如何实现这样的方法:
Transform Rotate90 = ??
这样Rotate90
顺时针旋转任何Translate
函数90。所以:
Point startPoint = new Point(1, 1);
Point endPoint = (Rotate90(forward))(startPoint);
//desired output: Point(1, 0)
编辑1:
我不打算逐一应用Translate
函数。我需要的是在一个点上应用一些已经被旋转或反射的变换函数(Translate
函数)。
我需要什么:如何写Rotate90
如果我通过它(p=>new Point(p.X+1, p.y))
它会返回一个效果与(p=>new Point(p.X, p.Y-1))
相同的函数。
编辑2:一些例子:
Translate forward = p => new Point(p.X + 1, p.Y);
Translate backward = p => new Point(p.X - 1, p.Y);
Translate downward = p => new Point(p.X, p.Y - 1);
Translate runningForward = p => new Point(p.X + 5, p.Y);
Transform Rotate90Cw = ??
Point samplePoint = new Point(1, 1);
Point p1 = (Rotate90Cw(forward))(samplePoint); //must be (1,0)
Point p2 = (Rotate90Cw(backward))(samplePoint); //must be (1,2)
Point p3 = (Rotate90Cw(downward))(samplePoint); //must be (0,1)
Point p4 = (Rotate90Cw(runningForward))(samplePoint); //must be (1,-4)
Point p4 = (Rotate90Cw(Rotate90Cw(forward)))(samplePoint); //must be (0,1)
我需要一个单个
Rotate90Cw
函数,可以应用于任何Translate
函数并返回正确的Translate
函数。因此,对点应用Rotate90Cw(forward)
的效果与在点上应用downward
的效果相同。等等...
我不会为每个案例制作单独的Rotate
函数(例如forwardRotated,downRotated和......
答案 0 :(得分:3)
目前尚不清楚你真的想要两位代表。看来你真的希望一个委托代表从Point
到Point
的任意转换 - 然后你可以组成转换。例如:
delegate Point Transform(Point input);
private static Transform Compose(Transform first, Transform second)
{
return p => second(first(p));
}
Transform forward = p => new Point(p.X + 1, p.Y);
Transform rotate90 = p => new Point(p.Y, -p.X);
Transform forwardThenRotate = Compose(forward, rotate);
编辑:看起来你真正想要的是一个变换(接受变换)的行:
我们可以轻松地做到这一点:
Transform forward = p => new Point(p.X + 1, p.Y);
Transform rotate90 = p => new Point(-p.Y, p.X);
Point forwardRotatedPoint = rotate90(forward(new Point(0, 0));
Transform forwardRotated = p => new Point(forwardRotatedPoint.X + p.X,
forwardRotatedPoint.Y + p.Y);
正如我在其他地方所说的那样,你可能实际上想要一个Vector
类型,它有X
和Y
个组件......那么你可能有几个可组合的概念:
答案 1 :(得分:0)
我这样解决(编辑):
Translate Rotate90Cw(Translate moveFunction)
{
return Rotate(moveFunction, Math.PI / 2.0);
}
Translate Rotate(Translate moveFunction, double angle)
{
Point tempPoint = moveFunction(new Point(0, 0));
double sin = Math.Sin(angle);
double cos = Math.Cos(angle);
return p => new Point(p.X + tempPoint.X * cos + tempPoint.Y * sin,
p.Y - tempPoint.X * sin + tempPoint.Y * cos);
}
检查它是否有效:
Rotate90Cw(Rotate90Cw(runningForward))(new Point(1, 1)); //output: (-4,0.9999999)
Rotate90Cw(runningForward)(new Point(1, 1)); //output: (1,-4)
Rotate90Cw(backward)(new Point(1, 1)); //output: (1,2)
Rotate90Cw(downward)(new Point(1, 1)); //output: (0,1)