Haskell：安装pureMD5软件包

Question

[我试图判断两个文件是否可能相同，发现我可以通过此StackOverflow线程在Haskell中进行MD5哈希：Compute MD5 digest of file in Haskell

[当我尝试安装pureMD5时，出现错误：

$ cabal install --lib pureMD5
Resolving dependencies...
cabal: Could not resolve dependencies:
[__0] trying: base-4.12.0.0/installed-4.1... (user goal)
[__1] trying: ghc-8.6.5/installed-8.6... (user goal)
[__2] next goal: process (user goal)
[__2] rejecting: process-1.6.6.0 (conflict: ghc =>
process==1.6.5.0/installed-1.6...)
[__2] rejecting: process-1.6.5.1, process-1.6.5.0/installed-1.6...,
process-1.6.5.0, process-1.6.4.0, process-1.6.3.0, process-1.6.2.0,
process-1.6.1.0, process-1.6.0.0, process-1.5.0.0, process-1.4.3.0,
process-1.4.2.0, process-1.4.1.0, process-1.4.0.0, process-1.3.0.0,
process-1.2.3.0, process-1.2.2.0, process-1.2.1.0, process-1.2.0.0,
process-1.1.0.2, process-1.1.0.1, process-1.1.0.0, process-1.0.1.5,
process-1.0.1.4, process-1.0.1.3, process-1.0.1.2, process-1.0.1.1,
process-1.0.0.0 (constraint from user target requires ==1.6.6.0)
[__2] fail (backjumping, conflict set: ghc, process)
After searching the rest of the dependency tree exhaustively, these were the
goals I've had most trouble fulfilling: process, base, ghc

我不确定从这里去哪里，我是Haskell的新手。

Answer 1

这是与pureMD5无关的阴谋论问题（我相信）。您可以尝试使用其他环境进行安装：

cabal new-install --package-env=SomeNewEnv --lib pureMD5

这应该起作用。但为什么？以及您当前已将软件包安装到的环境如下所示：
cat ~/.ghc/x86_64-darwin-8.6.4/environments/default | tail
package-id rts
package-id terminfo-0.4.1.2
package-id transformers-0.5.6.2
package-id deepseq-1.4.4.0
package-id ghc-boot-th-8.6.4
package-id pretty-1.1.3.6
package-id template-haskell-2.14.0.0
package-id directory-1.3.3.0
package-id txt-1.2.4.0-09ee5c37
package-id mtl-2.2.2

所以您会看到它修复了特定的软件包版本-对您来说，它可能会保留进程1.6.5.0。如果删除此文件，则将尝试成功安装process-1.6.6.0，并且安装将在没有--package-env的情况下进行。
再次，这是基于错误以及我认为您的系统状态而来的猜测-请进行测试并报告。
编辑：出于好奇，错误是https://github.com/haskell/cabal/issues/5559