[Haskell-cafe] foreach

[Lemmih]

On 9/13/06, Tim Newsham <newsham at lava.net> wrote:
> 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?

How about:

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

-- 
Cheers,
  Lemmih