Javran Cheng Javran

preservation and progress.

Javran / gist:3672733

Created September 8, 2012 08:13

an (stupid) attempt of adding logging function to State monad..

	import Control.Monad
	import Control.Monad.State

	type ListZipper a = ([a], [a])

	-- move focus forward, put previous root into breadcrumbs
	goForward :: ListZipper a -> ListZipper a
	goForward (x:xs, bs) = (xs, x:bs)

	-- move focus back, restore previous root from breadcrumbs

Javran / gist:3673869

Created September 8, 2012 11:29

use State monad and WriterT to implement ListZipper

	import Control.Monad
	import Control.Monad.State
	import Control.Monad.Trans.Writer

	type ListZipper a = ([a], [a])

	-- move focus forward, put previous root into breadcrumbs
	goForward :: ListZipper a -> ListZipper a
	goForward (x:xs, bs) = (xs, x:bs)

Javran / gist:3673898

Created September 8, 2012 11:30

use Writer monad and StateT to implement ListZipper

	import Control.Monad
	import Control.Monad.Writer
	import Control.Monad.Trans.State

	type ListZipper a = ([a], [a])

	-- move focus forward, put previous root into breadcrumbs
	goForward :: ListZipper a -> ListZipper a
	goForward (x:xs, bs) = (xs, x:bs)

Javran / gist:3719575

Created September 14, 2012 03:12

project euler p-104, why did this program eat up all my memory space?

	import Data.Char
	import Data.List

	fibSeq :: [(Integer, Integer)]
	fibSeq = map (\(n, (a,_)) -> (n, a)) $ iterate (\(n, (a,b))->(n+1, (b,a+b))) (1,(1,1))

	fstPandigital :: Integer -> Bool
	fstPandigital n = charNum == "123456789" where
	charNum = sort $ take 9 $ show n

Javran / gist:3728108

Created September 15, 2012 14:06

LYAH last assignment - a simple file system, using Either & WriterT

	import Data.List (break)
	import Control.Monad
	import Control.Monad.Instances
	import Control.Monad.Trans
	import Control.Monad.Trans.Writer

	type Name = String
	type Data = String

	data FSItem = File Name Data \| Folder Name [FSItem] deriving (Show)

Javran / gist:3765122

Created September 22, 2012 04:34

anonymous function in c++ !

	// compile with args: -lstdc++ -std=c++0x
	#include <cstdlib>
	#include <cstdio>

	#include <algorithm>
	#include <numeric>

	int a[16];

	int main()

Javran / gist:3794183

Created September 27, 2012 14:03

not-a-well-optimized solution for project euler p-14

	-- complied with: ghc --make problem-14 -rtsopts
	-- run with: ./problem-14 +RTS -K20000000 -RTS
	-- time elapsed: 32.592s


	import qualified Data.Set as S

	-- (set, (x,value))
	-- set: a set to keep numbers that has been calculated
	-- x: a number

Javran / gist:4022506

Created November 6, 2012 04:14

interface vs class itself

	public class Test {
	public static class A {}
	public static class B extends A {}
	public static class C extends A {}

	public interface Hello {
	void hello(A a);
	}

	public static class Tester implements Hello {

Javran / gist:4037813

Created November 8, 2012 09:41

refresh media lib

adb shell am start -a android.intent.action.MAIN -n com.android.development/.MediaScannerActivity

Javran / gist:4051704

Created November 10, 2012 16:58

....

	f = file( "raw", "r" )
	raw = f.read()
	f.close()

	secret = ''.join( map( lambda x:chr( int(x,2)) , map( lambda x: x.replace("____", "1111") , raw.split() ) ) ) + "="

	import base64

	g = file("sec", "wb")
	g.write( base64.b64decode( secret ) )