Haskell 如何处理重载多态性? [英] How does Haskell handle overloading polymorphism?
问题描述
我有一个关于 Haskell 多态性的问题.
据我所知,有两种类型的多态性:
参数:不指定输入类型.
例子:
函数名 :: [a] ->一个
重载:作为命令式编程,即将不同的参数传递给同一个函数.
我的问题是:Haskell 如何处理重载?
Haskell 中的重载是使用类型类完成的.例如,假设您要重载一个返回 Int
的函数 foo
:
class Fooable a wherefoo :: a ->诠释实例 Fooable Int 在哪里富=身份证instance Fooable Bool where富 _ = 42
但是,它们比大多数语言中的重载机制更强大.例如,您可以重载返回类型:
class Barable a where酒吧 :: Int ->一个实例 Barable Int 在哪里条 x = x + 3实例 Barable Bool where条 x = x <10
有关更多示例,请查看 Haskell 中的预定义类型类.p>
I have a question about Haskell polymorphism.
As I've learned, there are two types of polymorphism:
Parametric: where you do not specify the input type.
Example:
functionName :: [a] -> a
Overloading: as imperative programming, i.e. passing different arguments to the same function.
My problem is: how does Haskell handle overloading?
Overloading in Haskell is done using type classes. For example, let's say you want to overload a function foo
that returns an Int
:
class Fooable a where
foo :: a -> Int
instance Fooable Int where
foo = id
instance Fooable Bool where
foo _ = 42
However, they are more powerful than the overloading mechanisms found in most languages. For example, you can overload on the return type:
class Barable a where
bar :: Int -> a
instance Barable Int where
bar x = x + 3
instance Barable Bool where
bar x = x < 10
For more examples, have a look at the predefined type classes in Haskell.
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