haskell - flip fix / fix

Question

>>>flip fix (0 :: Int) (\\a b -> putStrLn \"abc\")
Output: \"abc\"

This is a simplified version of using flip fix.
I saw t

Answer 1

This is just a funny way to write a recursive lambda, I can think of two possibilities why this is done:

• The programmer wanted to confuse newbies.
• He comes from a language that is more restrictive with recursion (like some LISP, or ML maybe?)

You could rewrite the code much clearer like:

    loop secret 0
where
    loop secret numGuesses = do
         putStr "Guess: "
         guess <- getLine
         let
             score       = calcScore secret guess
             numGuesses' = numGuesses + 1
         print score
         case scoreRightPos score of
           4 -> putStrLn $ "Well done, you guessed in " ++ show numGuesses'
           _ -> loop secret numGuesses'

The difference being that you must pass the secret manually, which is avoided by the recursive lambda (and this might be another reason to write it with fix)

For a deeper understanding of fix, goog for "y-combinator"