Cabal不安裝基本版本4.7.0.0

Question

我需要Data.Either v。4.7.0.0的新函數「isLeft」，但cabal不安裝新庫。

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 

爲什麼會發生這種情況？

將基礎包升級到4.7版該怎麼做？

Answer 1

base是一個特殊的包。你不能升級它。如果你想要base-4.7，你必須使用GHC 7.8。