haskell传递参数中的映射

Question

如何在haskell中将Data.Map映射Int传递给[Char]？函数头如何？我们假设函数将返回一个int

import qualified Data.Map as M
someFunction :: <insert your answer here> -> Int

Answer 1

一个有效且可编辑的例子:

module Foo where
import qualified Data.Map as M
mapSize :: M.Map Int [Char] -> Int
mapSize m = M.size m

这让你做的事情,比如说GHCi

*Foo> let m = M.fromList [(2,"abc"), (3,"cde")] :: M.Map Int [Char]
*Foo> mapSize m
2