Scala，柯里化和重载 [英] Scala, currying and overloading

问题描述

假设您有以下内容:

foo(x: String)(y: Int): Int
foo(x: String)(y: Double): Int

Scala 不允许这样的表达.据我所知，原因是 foo("asdf") 没有明确定义的类型(它是 Int => Int 或 Double => Int).

Scala does not allow such expression. As far as I can see, the reason for this is that foo("asdf") does not have a well defined type (it's either Int => Int or Double => Int).

是否有理由不允许这种多类型"函数?

Is there a reason why such "polytyped" functions should not be allowed?

推荐答案

Scala 中的重载解析只考虑第一个参数列表.这就是为什么此列表中的替代方案必须有所不同的原因.这有一个很好的理由:然后我们可以使用解析函数的类型来推断后续参数的类型.这会启用以下习语:

Overloading resolution in Scala takes only the first parameter list into account. That's why alternatives must differ already in this list. There's a good reason for this: We can then use the resolved function's type to infer the type of subsequent arguments. This enables idioms like:

xs.corresponds(ys) { (x, y) => x < y }

注意这里我们需要知道corresponds的类型，以便推断x和y的类型.当 corresponds 超载时，这种崩溃将是一种耻辱.

Note that here we need to know the type of corresponds in order to infer the types of x and y. It would be a shame to have this break down when corresponds is overloaded.

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