haskell - yesod 安装失败

Question

我通常发现超过一半的大包的 cabal 安装失败，这对新用户来说是一个致命的缺陷!

这次我尝试安装yesod，有什么提示吗？

> cabal install yesod
  ...
Loading package time-1.2.0.5 ...

GHCi runtime linker: fatal error: I found a duplicate definition for symbol
   _get_current_timezone_seconds
whilst processing object file
   C:\Users\guthrie\AppData\Roaming\cabal\time-1.2.0.5\ghc-7.4.1\HStime-1.2.0.5.o
This could be caused by:
   * Loading two different object files which export the same symbol
   * Specifying the same object file twice on the GHCi command line
   * An incorrect `package.conf' entry, causing some object to be
     loaded twice.
GHCi cannot safely continue in this situation.  Exiting now.  Sorry.

cabal: Error: some packages failed to install:
authenticate-1.3.1.1 depends on http-conduit-1.6.1.1 which failed to install.
http-conduit-1.6.1.1 failed during the building phase. The exception was:
ExitFailure 1
yesod-1.1.1.2 depends on yesod-core-1.1.2.1 which failed to install.
yesod-auth-1.1.1.1 depends on yesod-core-1.1.2.1 which failed to install.
yesod-core-1.1.2.1 failed during the building phase. The exception was:
ExitFailure 1
yesod-form-1.1.3 depends on yesod-core-1.1.2.1 which failed to install.
yesod-json-1.1.0 depends on yesod-core-1.1.2.1 which failed to install.
yesod-persistent-1.1.0 depends on yesod-core-1.1.2.1 which failed to install.

Answer 1

yesod 使用与 Haskell 平台不同的 alex 包版本。除了 ghc 之外，我总是从发行版的软件包管理器中安装 alex 和 happy，然后使用 cabal。或者，您始终可以使用

cabal update && cabal install alex happy
cabal install yesod-platform