将浮点数转换为整数 [英] Converting Floating to Integer

问题描述

我试图定义：

I am trying to define:

square :: Integer -> Integer 
square = round . (** 2)

我得到：

and I am getting:

<interactive>:9:9: error:
    • No instance for (RealFrac Integer) arising from a use of ‘round’
    • In the first argument of ‘(.)’, namely ‘round’
      In the expression: round . (** 2)
      In an equation for ‘square’: square = round . (** 2)

<interactive>:9:18: error:
    • No instance for (Floating Integer)
        arising from an operator section
    • In the second argument of ‘(.)’, namely ‘(** 2)’
      In the expression: round . (** 2)
      In an equation for ‘square’: square = round . (** 2)

我在这种语言中仍然是新手，我似乎无法将浮点到整数的实例。有谁知道我该怎么做？

I am still new in this language and I seem to be unable to convert an instance of Floating to an Integer. Does anybody know how can I do so?

推荐答案

Haskell具有多种不同类型的指数函数：

Haskell has multiple exponent functions with different types:

• （^）::（Num a，Integral b）=> a - > b - > a


• （^^）::（小数a，积分b）=> a - > b - > a


• （**）:: Floating a => a - > a - > a

• (^) :: (Num a, Integral b) => a -> b -> a
• (^^) :: (Fractional a, Integral b) => a -> b -> a
• (**) :: Floating a => a -> a -> a

您正在寻找的那只是（ ^）。有了它，你甚至不需要 round ：

The one you are looking for is just (^). With it, you don't even need round:

square :: Integer -> Integer 
square = (^ 2)

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