在Go中输入变量

Question

In Haskell, map has type:

map :: (a -> b) -> [a] -> [b]

Note that a and b are not absolute types but type variables, which mean that they can be any type as long as each variable always refer to the same type in a specific function call. How to do the same thing in Go?

Answer 1

Go does not have a Hindley-Milner type system like Haskell's, so it can't express exactly the same things, like types with variables. The way type-agnostic functions are done in Go is with interfaces. If you want to express "any type", that's usually written as an empty interface (interface{}). The type of the Map function in the standard library is:

func Map(iter Iterable, f func(interface{}) interface{}) Iterable

So instead of taking a function that goes from a to b, it takes a function that goes from interface{} to interface{}.