Re: Indent for haskell

4 Apr 2006

      patc:
...
Is there an equivalent of an "indent" program for haskell?  I have a
bit of code I want to clean up ...
You could run your code through ghc, with -ddump-parsed turned on.
Then with a little bit of sed magic, you could recover the original code

Before:
    $ cat B.hs
    main = do  {
        ;print (f 10)
                ;      print (f 20)
       ;print (f 0xdeadbeef)
    }
    f x = sqrt  ( fromIntegral (x * 10133123 `mod` 1231111121 :: Int ))

After:
    $ ghc -fno-code -ddump-parsed B.hs

    ==================== Parser ====================
    main = do
             print (f 10)
             print (f 20)
             print (f 3735928559)
    f x = sqrt (fromIntegral ((x * 10133123) `mod` 1231111121 :: Int))

Postprocess:
    $ ghc -fno-code -ddump-parsed B.hs | sed '/^===/d'

    main = do
             print (f 10)
             print (f 20)
             print (f 3735928559)
    f x = sqrt (fromIntegral ((x * 10133123) `mod` 1231111121 :: Int))

Yay!

Now, I suspect there may be actually be (not well publicised) tools for this.
If there are, they should go on the haskell.org "Libraries and tools" page.

-- Don

dons＠cse.unsw.edu.au

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