为什么我的测试文件不导入我的数据结构？ Haskell

Question

我目前正在为我的（非常简单的）二十一点游戏编写单元测试，我的测试文件 (Tests.hs) 似乎没有导入我在文件中声明的数据结构，我正在为 ( HelpFunctions.hs)。我可以访问此文件中的 functions/methods 但不能访问数据结构。有人可以帮我找到问题吗？

这是我的测试文件的顶部：

module Tests(performTests) where
import Test.HUnit
import HelpFunctions

cardList = [(Hearts, Ace)]
(...)

这是我要为其编写测试的文件的顶部

module HelpFunctions(Suit, Value, blackjack, cardDeck, shuffleOne, 
                     shuffleCards, getValue, addHand, dealCard, bust, 
                     getHighest
                    ) where

import System.Random
import Control.Monad(when)

{- Suit is one of the four suits or color of a playing card 
   ie Hearts, Clubs, Diamonds or Spades
   INVARIANT: Must be one of the specified.
 -}
data Suit = Hearts | Clubs | Diamonds | Spades deriving (Show)

{- Value is the numeric value of a playing card according to the rules of blackjack. 
   INVARIANT: Must be one of the specified.
 -}
data Value = Two | Three | Four | Five | Six | Seven | Eight | 
             Nine | Ten | Jack | Queen | King | Ace 
             deriving (Eq, Show)
(...)

编译测试文件时出现错误

    Tests.hs:6:14: error: Data constructor not in scope: Hearts
  |
6 | cardList = [(Hearts, Ace)]   |              ^^^^^^

Tests.hs:6:22: error: Data constructor not in scope: Ace
  |
6 | cardList = [(Hearts, Ace)]   |                      ^^^

我有另一个文件从中导入 HelpFunctions 和数据结构，并且可以正常工作。

Answer 1

你的问题在这里：

module HelpFunctions(Suit, Value, ...

这一行说 HelpFunctions 导出类型 Suit 和 Value，但不导出它们的数据构造函数（即类型是抽象的）。

你想要

module HelpFunctions(Suit(..), Value(..), ...

您可以显式列出所有构造函数，但 .. shorthand 表示法表示 "all data constructors of this type".

参考：The Haskell 2010 Language Report, 5.2 Export Lists：

An algebraic datatype T declared by a data or newtype declaration may be named in one of three ways:

The form T names the type but not the constructors or field names. The ability to export a type without its constructors allows the construction of abstract datatypes (see Section 5.8).

The form T(c₁,…,c_n), names the type and some or all of its constructors and field names.

The abbreviated form T(..) names the type and all its constructors and field names that are currently in scope (whether qualified or not).

为什么我的测试文件不导入我的数据结构？ Haskell

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import

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hunit