I couldn't find a compile-time here document facility, so I wrote one using Template Haskell:
module HereDocs(hereDocs) where
import Control.Exception import Language.Haskell.TH.Syntax
getDoc :: String -> [String] -> (String,[String]) getDoc eof txt = let (doc,rest) = break (== eof) txt in (unlines doc, drop 1 rest)
makeVal :: String -> String -> [Dec] makeVal var doc = let name = mkName var in [SigD name (ConT (mkName "String")), ValD (VarP name) (NormalB (LitE (StringL doc))) []]
scanSrc :: [Dec] -> [String] -> Q [Dec] scanSrc vals [] = return vals scanSrc vals (x:xs) = case words x of [var, "=", ('<':'<':eof)] -> let (doc,rest) = getDoc eof xs val = makeVal var doc in scanSrc (vals ++ val) rest _ -> scanSrc vals xs
hereDocs :: FilePath -> Q [Dec] hereDocs src = let fin = catchJust assertions (evaluate src) (return.takeWhile (/= ':')) in runIO (fin >>= readFile >>= return . lines) >>= scanSrc []
One binds here documents embedded in comments by writing
import HereDocs $(hereDocs "Main.hs")
As an idiom, one can refer to the current file as follows; the first thing hereDocs does is catch assert errors in order to learn the file name:
import HereDocs $(hereDocs $ assert False "")
Here is an example use:
{-# OPTIONS_GHC -fth -Wall -Werror #-}
module Main where
import System import Control.Exception
import HereDocs $(hereDocs $ assert False "")
{- ruby = <
lisp = <
exec :: FilePath -> String -> IO ExitCode exec fout str = do writeFile fout str system ("chmod +x " ++ fout ++ "; ./" ++ fout)
main :: IO ExitCode main = do exec "hello.rb" ruby exec "hello.scm" lisp