我有以下Haskell代码
import Data.Int
import System.Environment
type Coord = (Int16, Int16)
distributePointsOverCircle :: Int16 -> Int16 -> [Coord]
distributePointsOverCircle points radius =
[ (xOf point, yOf point) | point <- [1..points] ]
where
xOf x = abstract cos x
yOf x = abstract sin x
abstract :: RealFrac a => ( a -> a ) -> Int16 -> Int16
abstract f x = (radius *) . truncate . f . fromIntegral $ (angleIncrement * x) * truncate (pi / 180)
angleIncrement = div 360 points
main = do
[a,b] <- getArgs
print $ distributePointsOverCircle (read a) (read b)
无论我传递给distributePointsOverCircle,它总是给我一个Coords的列表,因为我给出了每个Coord的第一个元素是半径而第二个元素为零的点。显然,这不是点的均匀分布。
我在这里做错了什么?是否有一些类型系统欺骗捏造我的数字?我试图用伪造的伪代码编写的函数是。
distributePointsOverCircle( numberOfPoints, radius )
angleIncrement = 360 / numberOfPoints
points = []
for i in 0 to (numberOfPoints -1)
p = Point()
p.x = (radius * cos((angleIncrement * i) * (PI / 180)))
p.y = (radius * sin((angleIncrement * i) * (PI / 180)))
points[i] = p
return points
答案 0 :(得分:5)
它为您提供了一个( r ,0)列表,因为truncate (pi / 180) == 0
。删除truncate
,代码应该可以正常工作。
abstract f x = (radius *) . truncate . f $ fromIntegral (angleIncrement * x) * (pi / 180)
答案 1 :(得分:2)
以下是我最终的结果:
import Data.Int
import System.Environment
type Coord = (Int16, Int16)
distributePointsOverCircle :: Int16 -> Int16 -> [Coord]
distributePointsOverCircle points radius =
[ (xOf point, yOf point) | point <- [1..points] ]
where
xOf x = abstract cos x
yOf x = abstract sin x
iRadius = fromIntegral radius
angleIncrement = div 360 points
abstract f x = round . (iRadius *) . f $ angle * (pi / 180)
where
angle = fromIntegral $ angleIncrement * x
main = do
[a,b] <- getArgs
print $ distributePointsOverCircle (read a) (read b)
正如已经提到的,问题是您在乘法之前使用了truncate,以便除其他事项truncate (pi / 180) == 0
之外。我还认为你的主要功能有一些错误。