David Tchepak dtchepak

dtchepak / ioexample.hs

Created June 15, 2012 07:00

IO example from Haskell.org IO tutorial (http://www.haskell.org/tutorial/io.html)

	-- IO example from http://www.haskell.org/tutorial/io.html
	-- copies one file to another:
	main = do fromHandle <- getAndOpenFile "Copy from: " ReadMode
	toHandle <- getAndOpenFile "Copy to: " WriteMode
	contents <- hGetContents fromHandle
	hPutStr toHandle contents
	hClose toHandle
	putStr "Done."

dtchepak / test.hs

Created June 4, 2012 00:27

Illegal instance declaration, flexible instances?

	{-# LANGUAGE MultiParamTypeClasses #-}
	class Collection c a where
	insert :: a -> c a -> c a

	instance Collection [] a where
	insert a b = (a:b)

	{-
	Illegal instance declaration for `Collection [] a'
	(All instance types must be of the form (T a1 ... an)

dtchepak / prob11_runlength.hs

Created May 22, 2012 03:03

Attempt at prob 11 from 99 Haskell probs

	import Data.List (group)

	data RunLength a = Single a \| Multiple Int a deriving (Show, Eq)

	encodeModified :: Eq a => [a] -> [RunLength a]
	encodeModified = map runLength . group
	where runLength [x] = Single x
	runLength xs@(x:_) = Multiple (length xs) x

dtchepak / cltd-typeclasses.hs

Created May 17, 2012 04:29

My attempt at solutions to data type and typeclasses sample probs


	-- Problem 1
	data NestedList a = Elem a \| List [NestedList a] deriving (Show,Eq)

	flatten :: NestedList a -> [a]
	flatten (Elem a) = [a]
	flatten (List []) = []
	flatten (List (h:t)) = flatten h ++ flatten (List t)

	-- Problem 2

dtchepak / splitWhere.hs

Created May 11, 2012 08:58

Attempt at splitting a single list into segments whenever a predicate is matched

	splitWhere :: [a] -> (a -> Bool) -> [[a]]
	splitWhere xs p = combine [] rest lists
	where
	(lists, rest) = foldr (\x (l,r) -> if p x then (combine [x] r l,[]) else (l,x:r)) ([],[]) xs
	combine [] [] c = c
	combine [] b c = b:c
	combine a [] c = a:c
	combine a b c = a:b:c

	-- Implementations below based on comments from #haskell IRC

dtchepak / Functors.cs

Created April 30, 2012 13:12

Attempt at C# Functors

	public static class Functors
	{
	public static IEnumerable<B> fmap<A,B>(this IEnumerable<A> functor, Func<A, B> f)
	{
	return functor.Select(f);
	}

	public static B? fmap<A, B>(this A? functor, Func<A, B> f) where A : struct where B : struct
	{
	return functor == null ? null : (B?) f(functor.Value);

dtchepak / fold2r.hs

Created March 5, 2012 09:07

folding over two lists

	fold2r :: (a -> b -> c -> c) -> c -> [a] -> [b] -> c
	fold2r f seed (a:as) (b:bs) = f a b (fold2r f seed as bs)
	fold2r _ seed _ _ = seed

	zipWithFold2r f = fold2r (\a b c -> (f a b):c) []

dtchepak / zipwith.hs

Created March 1, 2012 01:47

recursive zipwith

	zipWith' :: (a -> b -> c) -> [a] -> [b] -> [c]
	zipWith' _ [] _ = []
	zipWith' _ _ [] = []
	zipWith' f (a:as) (b:bs) = (f a b):(zipWith' f as bs)

dtchepak / zip.hs

Created February 29, 2012 12:27

Trying to implement zip using foldr

dtchepak / argh.hs

Created February 26, 2012 06:10

Playing around with take and fold

	data TakeState a = TakeState Int a deriving (Show)
	take' n =
	let f (TakeState i acc) head = if i==n then (TakeState i acc) else (TakeState (i+1) (acc++[head]))
	in foldl f (TakeState 0 [])