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 = <<RUBY
#!/usr/bin/env ruby
hello = <<EOF
Ruby is not
an acceptable Lisp
EOF
puts hello
RUBY
lisp = <<LISP
#!/usr/bin/env mzscheme -qr
(display #<<EOF
Lisp is not
an acceptable Haskell
EOF
)
(newline)
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
_______________________________________________
Haskell-Cafe mailing list
Haskell-Cafe@haskell.org
http://www.haskell.org/mailman/listinfo/haskell-cafe
