bayer:
I couldn't find a compile-time here document facility, so I wrote one
using Template Haskell:
Very nice! You should wrap it in a little .cabal file, and upload it to
hackage.haskell.org, so we don't forget about it.
Details on cabalising and uploading here:
http://haskell.org/haskellwiki/How_to_write_a_Haskell_program
http://cgi.cse.unsw.edu.au/~dons/blog/2006/12/11
-- Don
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
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