Desugarer

Desugars do-notation into infix applications of (>>=) and return. Just a fun adventure in SYB-land. Reads from stdin.

Suppose the file SumFile.hs contains the following snippet (from one of my first Haskell programs a few years back!):

-- SumFile.hs
sumFile :: IO ()
sumFile = do
            args <- getArgs
            if (not $ null args)
            then do
                contents <- readFile $ head args
                let ints = map read (lines contents) :: [Int]
                print $ foldr (+) 0 ints
            else return ()

It should walk the tree and pretty-print the desugared output.

$ desugar < SumFile.hs
sumFile :: IO ()
sumFile
  = getArgs >>=
      \ args ->
        if (not $ null args) then
          readFile $ head args >>=
            \ contents ->
              let ints = map read (lines contents) :: [Int] in
                print $ foldr (+) 0 ints
          else return ()

No support for -XArrows - I have no idea how they work and don't know how to desugar them properly.

thumphries/desugar

Desugarer