我在我的 centos 6 机器上安装了 ghc 和 cabal。两者似乎都运行正常。
但是当我尝试使用 cabal 安装 yesod 时，我得到了这个：
[root@localhost yesod]# cabal install yesod
Resolving dependencies...
cabal: cannot configure conduit-0.2.1. It requires base >=4.3 && <5
For the dependency on base >=4.3 && <5 there are these packages: base-4.3.0.0,
base-4.3.1.0, base-4.4.0.0, base-4.4.1.0 and base-4.5.0.0. However none of them are available.
base-4.3.0.0 was excluded because yesod-auth-0.8.1.1 requires base >=4 && <4.3
base-4.3.0.0 was excluded because yesod-core-0.10.1 requires base >=4 && <4.3
base-4.3.0.0 was excluded because yesod-0.10.1 requires base >=4 && <4.3
base-4.3.0.0 was excluded because of the top level dependency base -any
base-4.3.1.0 was excluded because yesod-auth-0.8.1.1 requires base >=4 && <4.3
base-4.3.1.0 was excluded because yesod-core-0.10.1 requires base >=4 && <4.3
base-4.3.1.0 was excluded because yesod-0.10.1 requires base >=4 && <4.3
base-4.3.1.0 was excluded because of the top level dependency base -any
base-4.4.0.0 was excluded because yesod-auth-0.8.1.1 requires base >=4 && <4.3
base-4.4.0.0 was excluded because yesod-core-0.10.1 requires base >=4 && <4.3
base-4.4.0.0 was excluded because yesod-0.10.1 requires base >=4 && <4.3
base-4.4.0.0 was excluded because of the top level dependency base -any
base-4.4.1.0 was excluded because yesod-auth-0.8.1.1 requires base >=4 && <4.3
base-4.4.1.0 was excluded because yesod-core-0.10.1 requires base >=4 && <4.3
base-4.4.1.0 was excluded because yesod-0.10.1 requires base >=4 && <4.3
base-4.4.1.0 was excluded because of the top level dependency base -any
base-4.5.0.0 was excluded because yesod-auth-0.8.1.1 requires base >=4 && <4.3
base-4.5.0.0 was excluded because yesod-core-0.10.1 requires base >=4 && <4.3
base-4.5.0.0 was excluded because yesod-0.10.1 requires base >=4 && <4.3
base-4.5.0.0 was excluded because of the top level dependency base -any
更新：刚刚尝试安装 haskell-platform，看看是否能解决依赖性问题，但没有成功。当我运行cabal install Cabal cabal-install yesod