Haskell如何解决此错误: Unsupported extension: MultiWayIf

Question

尝试安装friday软件包时，出现错误

Preprocessing library friday-0.2.2.0...

src/Vision/Detector/Edge.hs:3:14: Unsupported extension: MultiWayIf
cabal: Error: some packages failed to install:
friday-0.2.2.0 failed during the building phase. The exception was:
ExitFailure 1

如何解决这个错误？

我正在使用 ghc 版本 7.4.1 和

cabal-install version 0.14.0
using version 1.14.0 of the Cabal library 

Answer 1

MultiWayIf 是在 GHC 7.6 分支中引入的。您将必须升级编译器或修补库。