[Haskell-cafe] foreach

13 Sep 2006

      I was rewriting some non-haskell code in haskell and came up with this 
construct:

   foreach l f = mapM_ f l

   main = do
       args <- getArgs
       foreach args (\arg -> do
           foreach [1..3] (\n -> do
               putStrLn ((show n) ++ ") " ++ arg)
            )
        )

which is reminiscent of foreach in other languages.  Seems fairly
useful and I was wondering how hard it would be to add some syntactic
sugar to the "do" construct to make it a little prettier (ie.
not require the parenthesis, binding and nested do, as:

   main = do
       args <- getArgs
       foreach args arg
           foreach [1..3] n
               putStrLn ((show n) ++ ") " ++ arg)

would this type of transformation be possible with template haskell
or does this need stronger support from the parser to pull off?

Tim Newsham
http://www.thenewsh.com/~newsham/