Studieren Sie das Papier zu Schleifen in Haskell und lösen Sie die dort enthaltenen Aufgaben.
> module Loop where
> import Data.Char
> for result test step calcResult v
> |test v = for (calcResult result v) test step calcResult (step v)
> |otherwise = result
> fac1 = for 1 (\x-> x>0) (\x->x-1) (*)
> sum1 = for 0 (not.null) tail (\r xs -> r+head xs)
> len1 = for 0 (not.null) tail (\r _ -> r+1)
> rev1 = for [] (not.null) tail (\r xs -> head xs:r)
> for2 result test step calcResult v
> |test v = (for2$!(calcResult result v)) test step calcResult (step v)
> |otherwise = result
> fac3 = for2 1 (\x-> x>0) (\x->x-1) (*)
> fac2 n
> |n<=0 = 1
> |otherwise = n*fac (n-1)
> sum2 [] = 0
> sum2 (x:xs) = x+sum xs
> max2 [x] = x
> max2 (x:xs) = max x (max2 xs)
> fi2 _ [] = []
> fi2 p (x:xs)
> |p x = x:fi2 p xs
> |otherwise = fi2 p xs
> type TestFunction a = a -> Bool
> type BaseResult a r = a -> r
> type ResultFunction a r = a -> r -> r
> type StepFunction a = a -> a
> loop ::
> TestFunction a
> -> BaseResult a r
> -> ResultFunction a r
> -> StepFunction a
> -> a
> -> r
> loop p baseResultF resultF step v
> |p v = baseResultF v
> |otherwise = resultF v (loop p baseResultF resultF step (step v))
> fac = loop ((>=) 0) (const 1) (*) (\x->x-1)
> len = loop null (const 0) (\_ y -> y+1) tail
> ma :: Ord a => [a] -> a
> ma = loop (null.tail) head (\xs m -> max (head xs) m) tail
> fi p = loop null id (\x y ->if p(head x) then (head x:y) else y) tail
> la = loop (null.tail) head (\_ y -> y) tail
> re = loop null id (\x r -> r++[head x]) tail
> from = loop (\x->False) (const []) (\x rs -> x:rs) ((+) 1)
> fromTo frm to = loop (\x->x>to) (const []) (\x rs -> x:rs) ((+) 1)frm
Hier die Aufgaben aus dem Papier:
> quersumme n = 0
> readNumber = const 0
> toBinary = const ""
> contains o = const False
> ma1 f = const []
> sieb2 = const []
> woerter = snd.result " ".loop null (const ([],[])) result tail
> where
> result (x:xs) (w,ws) = ([],[])
Subato
