Question

你好，我想知道你如何解决Haskell中的循环依赖

我有：
类型的模块。

module Company where

import Tclass

data Worker=Worker{
    age::Int,
    name::String,
    title::Title,
    income::Int
}

data Title=Manager | Dev | Tester deriving (Show)


data Company=Company{
    cname::String,
    people::[Worker],
    yf::Int
}

类型类实例的模块

module Tclass where
import System.Environment
import Company

class Console a where
    wLine::a->IO()
    rLine::IO String->a

instance Show Worker where
    show w="to be defined"
    print =putStr . show

如果我只想在ghci中加载类型并使用它；如何导入它们而不会出现错误：

Module imports form a cycle:
         module `Tclass' (.\Tclass.hs)
        imports `Company' (Company.hs)
  which imports `Tclass' (.\Tclass.hs)

PS 我尝试创建一个辅助模块来导入两个模块，而这两个模块也可以导入它，但是这两个模块也没有运气：

module Au where
 import Tclass
 import Company

module Company
 import Au

module Tclass 
 import Au

Answer 1

将Show实例移至其他模块，可以中断周期：

module Tclass where
import System.Environment
import Company

class Console a where
    wLine::a->IO()
    rLine::IO String->a

和

module Company where

data Worker=Worker{
    age::Int,
    name::String,
    title::Title,
    income::Int
}
instance Show Worker where
    show w="to be defined"
    print =putStr . show 

data Title=Manager | Dev | Tester deriving (Show)

data Company=Company{
    cname::String,
    people::[Worker],
    yf::Int
}

模块导入形成一个循环

1 个答案: