Hi,
Following code is to get a list of primes. Now it is hard for me to understand funB. I mean I can see what it does. But I cannot see the detailed process by every language part. import Control.Monad isPrime :: Integer -> Bool isPrime i = ap funA funB i funA :: Integer -> [Integer] -> Bool funA x xs = all (\x' -> (mod x x') /= 0) xs funB :: Integer -> [Integer] funB = flip takeWhile primes . ( . join (*)) . flip (<=) primes :: [Integer] primes = 2 : filter isPrime [3, 5 ..] main :: IO () main = print $ take 10 primes _______________________________________________ Haskell-Cafe mailing list [hidden email] http://www.haskell.org/mailman/listinfo/haskell-cafe |
funB = flip takeWhile primes . ( . join (*)) . flip (<=) funB x = flip takeWhile primes ((( . join (*)) . flip (<=)) x) funB x = takeWhile ((( . join (*)) . flip (<=)) x) primes funB x = takeWhile (foo x) primes foo x = (( . join (*)) . flip (<=)) x foo x = (( . join (*)) (flip (<=) x) foo x = flip (<=) x . join (*) foo x = (x <=) . join (*) -- join :: Monad m => m (m a) -> m a -- join (*) == (**2) foo x = (x <=) . (** 2) foo x y = x <= (y ** 2) isLessThanTheSquareOf = foo funB x = takeWhile (x `isLessThanTheSquareOf`) primes Helpful? On Fri, Dec 19, 2014 at 2:52 PM, Magicloud Magiclouds <[hidden email]> wrote:
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Thank you. This will take some time for me to read. On Fri, Dec 19, 2014 at 12:32 PM, Lyndon Maydwell <[hidden email]> wrote:
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I suspect that somebody has been abusing pointfree. On Thu, Dec 18, 2014 at 8:35 PM, Magicloud Magiclouds <[hidden email]> wrote:
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I do not think pointfree works here: Transformed to pointfree style: funB = id (fix (const (flip takeWhile primes . (. join (*)) . flip (<=)))) Optimized expression: funB = id (fix (const (flip takeWhile primes . (. join (*)) . flip (<=)))) funB = fix (const (flip takeWhile primes . (. join (*)) . flip (<=))) funB = flip takeWhile primes . (. join (*)) . flip (<=) On Sat, Dec 20, 2014 at 1:21 AM, Alex Hammel <[hidden email]> wrote:
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