GHC在cabal沙箱中找不到模块

我在(X)Ubuntu 15.10上使用Haskell版本7.8.4,同时安装了Cabal-Install 1.18 apt.我没有尝试在这台机器上手动安装任何与Haskell相关的东西.我设置了一个cabal沙箱,取出并安装了一个模块,ghc但却发现它似乎没有被捡起来.ghc -v似乎暗示我有两个版本的cabal库相互遮蔽.这是如何运作的？

我开始时是一个空目录 /tmp/haskell-example

然后我做了cabal sandbox init.

$ cabal sandbox init
Writing a default package environment file to
/tmp/haskell-example/cabal.sandbox.config
Creating a new sandbox at /tmp/haskell-example/.cabal-sandbox

然后我安装,natural-numbers因为我想Data.Natural在程序中使用该模块.此操作成功.

$ cabal install natural-numbers
Resolving dependencies...
Notice: installing into a sandbox located at
/tmp/haskell-example/.cabal-sandbox
Configuring natural-numbers-0.1.2.0...
Building natural-numbers-0.1.2.0...
Installed natural-numbers-0.1.2.0

我可以验证Data.Natural模块是否确实安装在cabal沙箱中.

$ ls /tmp/haskell-example/.cabal-sandbox/lib/x86_64-linux-ghc-7.8.4/natural-numbers-0.1.2.0
 Data
libHSnatural-numbers-0.1.2.0.a
libHSnatural-numbers-0.1.2.0-ghc7.8.4.so
$ ls /tmp/haskell-example/.cabal-sandbox/lib/x86_64-linux-ghc-7.8.4/natural-numbers-0.1.2.0/Data
Natural.dyn_hi
Natural.hi

然后我创建一个Main.hs导入Data.Natural但不使用它的简单文件.

module Main where

import Data.Natural

main = putStrLn "Hello World"

当我尝试时,ghc Main.hs我看到以下内容:

$ ghc Main.hs 
Main.hs:3:8:
    Could not find module ‘Data.Natural’
    Use -v to see a list of the files searched for.

随着启用详细标记,似乎我的阴谋被后来的阴影所遮蔽,这反过来影响了早期的阴谋集团.为什么会这样？

$ ghc -v Main.hs 
Glasgow Haskell Compiler, Version 7.8.4, stage 2 booted by GHC version 7.8.4
Using binary package database: /usr/lib/ghc/package.conf.d/package.cache
hiding package Cabal-1.18.1.5 to avoid conflict with later version Cabal-1.22.1.1
wired-in package ghc-prim mapped to ghc-prim-0.3.1.0-ec14d2f6075975a2ce9112eae431c8e1
wired-in package integer-gmp mapped to integer-gmp-0.5.1.0-de4898ebdc5ab81cedce89121ae9ac84
wired-in package base mapped to base-4.7.0.2-5ef1e7e809bc3b18d74efc783356e209
wired-in package rts mapped to builtin_rts
wired-in package template-haskell mapped to template-haskell-2.9.0.0-c1976a420ad8b9b589eee08844c59ba2
wired-in package dph-seq not found.
wired-in package dph-par not found.
Hsc static flags: 
hiding package Cabal-1.18.1.5 to avoid conflict with later version Cabal-1.22.1.1
wired-in package ghc-prim mapped to ghc-prim-0.3.1.0-ec14d2f6075975a2ce9112eae431c8e1
wired-in package integer-gmp mapped to integer-gmp-0.5.1.0-de4898ebdc5ab81cedce89121ae9ac84
wired-in package base mapped to base-4.7.0.2-5ef1e7e809bc3b18d74efc783356e209
wired-in package rts mapped to builtin_rts
wired-in package template-haskell mapped to template-haskell-2.9.0.0-c1976a420ad8b9b589eee08844c59ba2
wired-in package dph-seq not found.
wired-in package dph-par not found.
*** Chasing dependencies:
Chasing modules from: *Main.hs

Main.hs:3:8:
    Could not find module ‘Data.Natural’
    Locations searched:
    Data/Natural.hs
    Data/Natural.lhs
*** Deleting temp files:
Deleting: 
*** Deleting temp dirs:
Deleting: 

sinelaw.. 7

如果您正在进行手动黑客攻击,则可以将沙箱的pkg db位置传递给ghc,例如:

ghc Main.hs -package-db .cabal-sandbox/x86_64-linux-ghc-7.10.2-packages.conf.d/

但是,使用沙箱的"常规"方法是始终使用cabal build(或cabal install不使用参数)进行编译,而不是直接运行ghc.

跑cabal init,回答你的问题

编辑生成的foo.cabal文件(foo是包的名称).

运行cabal build或cabal install- 这将为您运行ghc.

编辑cabal文件时,检查导出的模块(如果是lib)是否已列出,并且主src是否正确.还要确保子句natural-numbers中列出的依赖项build-depends:.

1> sinelaw..：

---

如果您正在进行手动黑客攻击,则可以将沙箱的pkg db位置传递给ghc,例如:

ghc Main.hs -package-db .cabal-sandbox/x86_64-linux-ghc-7.10.2-packages.conf.d/

但是,使用沙箱的"常规"方法是始终使用cabal build(或cabal install不使用参数)进行编译,而不是直接运行ghc.

跑cabal init,回答你的问题

编辑生成的foo.cabal文件(foo是包的名称).

运行cabal build或cabal install- 这将为您运行ghc.

编辑cabal文件时,检查导出的模块(如果是lib)是否已列出,并且主src是否正确.还要确保子句natural-numbers中列出的依赖项build-depends:.

---

等一等.我想我完全错误地想到了"阴谋".我期待一个cabal沙箱的行为像virtualenv或npm环境并改变ghc的行为,但似乎唯一的相似之处在于它重定向`cabal install`安装的东西.这现在非常有意义.