fixes for haskellng + add example

README.md

@@ -25,7 +25,7 @@ Usage
 To use `nix-script`, you need to add a header to your file. Here is an example for a haskell file `example.hs`:
 
 ```haskell
-#!nix-script
+#!/usr/bin/env nix-script
 #!> haskell
 #! haskell | text lens optparse-applicative
 #! shell   | nix nix-prefetch-scripts

example.hs

@@ -0,0 +1,8 @@
+#!/usr/bin/env nix-script
+#!> haskell
+#! haskell | text lens optparse-applicative
+#! shell | nix nix-prefetch-scripts
+
+main :: IO ()
+main = do
+  putStrLn "It works!"

nix-script.hs

@@ -1,4 +1,4 @@
-#!nix-bang
+#!/usr/bin/env nix-script
 #!> haskell
 #! haskell | text lens
 #! shell   | nix
@@ -37,8 +37,7 @@ languages = [haskell, shell]
 haskell :: LangDef
 haskell = LangDef "haskell" d r i where
   d pkgs = return $
-    "haskellPackages.ghcWithPackages (hs: with hs; [" <> Text.unwords (map mkPkg pkgs) <> "])"
-  mkPkg = Text.concat . over (_tail.mapped._head) toUpper . Text.splitOn "-"
+    "haskellPackages.ghcWithPackages (hs: with hs; [" <> Text.unwords pkgs <> "])"
   r script = ("runhaskell" , [script])
   i script = ("ghci"       , [script])