GHC无法在新安装的Haskell-Platform上找到库 [英] GHC cannot find libraries on fresh install of Haskell-Platform

问题描述

我试图学习如何使用Haskell，但我碰到了一个小小的障碍。我正在使用MacOSX 10.12.6并安装了Haskell Platform：

  $ brew cask install haskell-platform 
  

不作任何修改。当我尝试使用 parsec 导入时编译程序时，Haskell-Platform无法找到它：

  $ ghc -v test.hs 
 ... 
软件包parsec-3.1.11-DPgnR92AWEaFOaixmwipet由于被隐藏的依赖关系而不可用：
 mtl-2.2.1- 19EL8AGBsN3DnnOhrC9xY3 text-1.2.2.2-EGUst8sqNAZCw1xLPcmcMH 
 ... 
 test.hs：2：1：error：
无法找到模块'Text.Parsec'
搜索的位置：
 Text / Parsec.hs 
 Text / Parsec.lhs 
 Text / Parsec.hsig 
 Text / Parsec.lhsig 
 | 
 2 |导入Text.Parsec 
 | ^^^^^^^^^^^^^^^^^^ 
  

安装了parsec ：

  $ ghc-pkg list | grep -e'parsec'
 attoparsec-0.13.2.0 
 parsec-3.1.11 
  

所以我有几个问题：

• 阴影依赖是什么意思？


• GHC在哪里查找库？


• GHC在哪里查找用户库和系统范围库？


• 这条路可以修改吗？
平台的构建，并发布了一个新版本，以解决您遇到的问题。




该错误的详细信息以及新版本均在 https://mail.haskell.org/pipermail/haskell-cafe/2017-October/127979 .html




I'm trying to learn how to use Haskell, but I've run into a little roadblock. I'm using MacOSX 10.12.6 and installed Haskell Platform using:

$ brew cask install haskell-platform

with no modifications. When I try to compile a program with parsec imported, Haskell-Platform can't find it:

$ ghc -v test.hs 
...
package parsec-3.1.11-DPgnR92AWEaFOaixmwipet is unusable due to shadowed dependencies:
mtl-2.2.1-19EL8AGBsN3DnnOhrC9xY3 text-1.2.2.2-EGUst8sqNAZCw1xLPcmcMH
...
test.hs:2:1: error:
    Could not find module ‘Text.Parsec’
    Locations searched:
    Text/Parsec.hs
    Text/Parsec.lhs
    Text/Parsec.hsig
    Text/Parsec.lhsig
|
2 | import Text.Parsec
| ^^^^^^^^^^^^^^^^^^

parsec is installed:

$ ghc-pkg list | grep -e 'parsec'
attoparsec-0.13.2.0
parsec-3.1.11

So I have a few questions:

• What does it mean by shadowed dependencies?
• Where does GHC look for libraries?
• Where does GHC look for user libraries vs system wide libraries?
• Can this path be modified?

解决方案

There was a bug with 8.2.1 binary platform builds, and a new release was cut to fix the issue you encountered.

Details on the bug, and the new release are provided at https://mail.haskell.org/pipermail/haskell-cafe/2017-October/127979.html

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