我需要 Data.Either v. 4.7.0.0 的新函数“isLeft”,但 cabal 没有安装新库。
Microsoft Windows [Version 6.1.7601]
Copyright (c) 2009 Microsoft Corporation. All rights reserved.
C:\Users\Alberto>cabal update
Downloading the latest package list from hackage.haskell.org
Note: there is a new version of cabal-install available.
To upgrade, run: cabal install cabal-install
C:\Users\Alberto>cabal install base
Resolving dependencies...
All the requested packages are already installed:
base-4.6.0.1
Use --reinstall if you want to reinstall anyway.
C:\Users\Alberto>date
The current date is: 19/04/2014
为什么会发生这种情况?
如何将基础包升级到版本 4.7?
最佳答案
base
是一个特殊的包。您无法升级它。如果您想要 base-4.7,则必须使用 GHC 7.8。
关于haskell - Cabal 未安装 4.7.0.0 版本的 base,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/23173714/