The Evolution Ofa Haskell Programmer

See http://www.willamette.edu/~fruehr/haskell/evolution.html for various interesting applications of the HaskellLanguage. Proves that ThereIsMoreThanOneWayToDoIt in HaskellLanguage, and that HaskellCanBeAsGoodAsPerl? (well, not really).

I think of this as the ObfuscatedPerl contest meets MathematicsMadeDifficult?. The later versions are all based on ludicrously overpowered excursions into CategoryTheory.

Somebody in OnMonads pointed out that the above document doesn't have a monadic factorial, so I will provide one. One imagines that this would be written by someone who came from an asm background...
    slice :: [a] -> Int -> Int -> [a]
    slice _ _ 1 = []
    slice x:xs 0 end = x : (slice xs 0 (end - 1))
    slice x:xs beg end = slice xs (beg - 1) (end - 1)

data Variable = Var Int data Scope = [Int] data ScopeFn? a = Scope -> (a, Scope) deriving Monad; new :: ScopeFn? Variable new scope fn = fn ((Var (length scope)), scope) set :: Variable -> Int -> ScopeFn? () set (Var x) value scope fn = fn ((), ((slice scope 0 x) ++ [value] ++ (slice scope (x + 2) (length scope)))) get :: Variable -> ScopeFn? Int get (Var x) scope fn = fn (scope !! x, scope)

(>>=) :: ScopeFn? a -> (a -> ScopeFn? b) -> ScopeFn? b (>>=) fn1 fn2 scope1 = let (value, scope2) = fn1 scope1 in fn2 value scope2 return :: a -> ScopeFn? a return x scope = (x, scope)

prod :: Variable -> Variable -> Variable -> ScopeFn? () prod res a b = do a' = get a b' = get b set res (a' * b') dec :: Variable -> ScopeFn? () dec v = do v' = get v set v (v' - 1) inScope :: ScopeFn? a -> a inScope fn = ret where (ret, _) = fn []

fac :: Int -> Int fac' x y = do prod x x y dec y y' <- get y if (y' == 0) then return () else fac' x y

fac x = inScope do total <- new va <- new set va x set total 1 fac' total va ret <- get va return va


CategoryFunctionalProgramming CategoryHaskell

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