I'm just getting started using the glasgow haskell compiler and when I try to compile a simple program, named Hello.lhs, like this:

module Main (main) where main = putStrLn "Hello World" end

with the command

ghc Hello.lhs

I get the message on standard output:

No definitions in file <perhaps you forgot the '>'s?>

The extension '.lhs' means "Literate Haskell source" which is described here: http://www.haskell.org/onlinereport/literate.html Normal Haskell source files, like the code example you give above, should be placed in a file with a '.hs' extension. Cheers, Simon