I'm using Windows 7 with cygwin too.
I'd installed happstack-hsp fine with the Haskell Platform from February.
I just installed the Haskell Platform from April. I tried installing happstack-hsp package, through cabal and get the following error:
$cabal install happstack-hsp
Resolving dependencies...
Configuring hsp-0.7.1...
Building hsp-0.7.1...
Preprocessing library hsp-0.7.1...
ghc.exe: could not execute: trhsx
cabal.exe: Error: some packages failed to install:
happstack-hsp-7.1.1 depends on hsp-0.7.1 which failed to install.
hsp-0.7.1 failed during the building phase. The exception was:
ExitFailure 1
I tried to to then install trhsx, and got this error:
$cabal install trhsx
Resolving dependencies...
Configuring trhsx-0.2.2...
Building trhsx-0.2.2...
Preprocessing library trhsx-0.2.2...
Trhsx.hs:1:1:
Could not find module `Prelude'
It is a member of the hidden package `base'.
Perhaps you need to add `base' to the build-depends in your .cabal file.
It is a member of the hidden package `haskell2010-1.1.0.1'.
Perhaps you need to add `haskell2010' to the build-depends in your .cabal file.
It is a member of the hidden package `haskell98-2.0.0.1'.
Perhaps you need to add `haskell98' to the build-depends in your .cabal file.
Use -v to see a list of the files searched for.
cabal.exe: Error: some packages failed to install:
trhsx-0.2.2 failed during the building phase. The exception was:
ExitFailure 1
I tried this in cmd too, and got the same outcome. It's been many years since I used haskell, and it's changed quite a bit, any ideas?
trhsx comes from the hsx package now. The reason for the error is that cabal installs the executable in $HOME/.cabal/bin by default. But, $HOME/.cabal/bin is not in your $PATH by default.
If you add that to your $PATH, then everything should be ok.