隐藏来自GHCi的随机版本 [英] Hiding versions of random from GHCi

问题描述

我正在使用 newsynth 包，并且遇到了一个错误，我开始怀疑它与整个夏天的更新 random-1.2.0 有关.( newsynth 的最新更新时间为2019年末， random-1.2.0 于6月发布.此后，我一直运行 cabal update ，这就是为什么两者似乎都安装的原因.)这是我在GHCi中运行的代码:

I am working with the newsynth package and am running into a bug that I am starting to suspect has to do with the update random-1.2.0 over the summer (newsynth was last updated in late 2019, and random-1.2.0 came out in June. I have run cabal update since then, which is why both seem to be installed.) Here is the code that I ran in GHCi:

 λ> import System.Random
 λ> import Quantum.Synthesis.Ring
 λ> import Quantum.Synthesis.Diophantine
 λ> g <- getStdGen
 λ> diophantine g (RootTwo 5 0)

<interactive>:5:1: error:
    • No instance for (random-1.1:System.Random.RandomGen StdGen)
        arising from a use of ‘diophantine’
      There are instances for similar types:
        instance random-1.1:System.Random.RandomGen
                   random-1.1:System.Random.StdGen
          -- Defined in ‘random-1.1:System.Random’
    • In the expression: diophantine g (RootTwo 5 0)
      In an equation for ‘it’: it = diophantine g (RootTwo 5 0)

正如在另一篇SO帖子中向我建议的那样，我尝试从GHCi隐藏 random 的另一个副本.我跑了

As was suggested to me in another SO post, I tried hiding the other copy of random from GHCi. I ran

$ ghc-pkg --global --package-db ~/.cabal/store/ghc-8.8.3/package.db list random
~/.ghcup/ghc/8.8.3/lib/ghc-8.8.3/package.conf.d
    (no packages)
~/.cabal/store/ghc-8.8.3/package.db
    random-1.1
    random-1.2.0

所以我尝试了 $ ghc-pkg --global --package-db〜/.cabal/store/ghc-8.8.3/package.db隐藏random-1.2.0 .但是，当错误仍然存​​在时，我也尝试了 $ ghc-pkg --global --package-db〜/.cabal/store/ghc-8.8.3/package.db hide random-1.1 (只是为了确保 hide 达到了我的预期)，但莫名其妙地发现，在GHCi中(即使在重新启动Terminal之后)我也可以运行λ>.尽管隐藏了 random 的所有已知实例，但仍要导入System.Random .我会以错误的方式隐藏包裹吗?

so I tried $ ghc-pkg --global --package-db ~/.cabal/store/ghc-8.8.3/package.db hide random-1.2.0. However, when the bug persisted, I also tried $ ghc-pkg --global --package-db ~/.cabal/store/ghc-8.8.3/package.db hide random-1.1 (just to make sure hide did what I thought it would), yet inexplicably found that in GHCi (even after restarting Terminal) I was able to run λ> import System.Random despite all known instances of random being hidden. Am I hiding packages in the wrong way?

谢谢.

(前几天我问了一个相关的问题，但由于我认为这个问题有点不同，所以我认为将其分开是有意义的.如果不是这种情况，我可以更新另一篇文章.)

(I asked a somewhat related question the other day but since I think this issue is kinda different I thought it made sense be separate. If this is not the case I can update the other post.)

推荐答案

当您要管理软件包时，请使用cabal或stack.但首先，重置为干净状态:

Use cabal or stack when you want to manage packages. But first, reset to clean state:

rm -rf ~/.ghc ~/.cabal
cabal update
cabal v2-repl -b newsynth

这将使您进入GHCi会话并获得所需的软件包.

This will get you into a GHCi session with the desired package available.

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