I tried installing the haskell platform and yesod from scratch, but it failed during the installation of double-conversion-0.2.0.0 with the following error:

Loading package double-conversion-0.2.0.0 ... <command line>: can't load .so/.DLL for: stdc++ (dlopen(libstdc++.dylib, 9): image not found)

cabal: Error: some packages failed to install:

yesod-auth-0.6.0 failed during the building phase. The exception was:

ExitFailure 1