从Num实施复杂

Question

我是Haskell的新手,想学习如何从Num类实现我的复数.

data Complex = Complex{x::Float, y::Float} deriving (Show)

instance Num Complex where
        (Complex x1 y1) + (Complex x2 y2) = Complex(x1 + x2) (y1 + y2)
        (Complex x1 y1) - (Complex x2 y2) = Complex(x1 - x2) (y1 - y2)
        (Complex x1 y1) * (Complex x2 y2) = Complex(x1*x2 - y1*y2) (x1*y2 + x2*y2)
        fromInteger n                     = Complex(fromInteger n) (fromInteger n) 
        signum (Complex x y)              = Complex(signum x) (signum y) 
        abs (Complex x y)                 = Complex(abs x) (abs y) 

我的问题是如何使用

fromInteger n = Complex(fromInteger n) (fromInteger n)

Answer 1

以下是fromInteger在GHCi 中使用该函数的两个示例:

?> fromInteger 5 :: Complex
Complex {x = 5.0, y = 5.0}

?> :set -XTypeApplications

?> fromInteger @Complex 5
Complex {x = 5.0, y = 5.0}

顺便说一句,我相信你有错误的实施.查看源代码,看看它是如何完成的base.它似乎应该被定义为:

fromInteger n = Complex (fromInteger n) 0