module C9 where

import System.Random
import Debug.Trace

-- fibb 25
fibb n = case n of
	0 -> 1
	1 -> 1
	_ -> fibb (n - 1) + fibb (n - 2)
	
-- take fibbF 30
fibbF = 1 : 1 : zipWith (+) fibbF (tail fibbF)
	
-- x - ultimul element din sir
-- y - penultimul element din sir
fibbT n = fibbTR 1 1 n
	where fibbTR x y n = 
		trace (concat $ map ((++" ").show) [n,x,y]) $
			if n == 0 then x else fibbTR (x + y) x (n - 1)
	
fibbM n = fibbMHelp n [] !! n where
	fibbMHelp n fibbs = case n of
		0 -> [1]
		1 -> [1]
		_ -> fibbs ++ [fibbs !! (n - 1) + fibbs !! (n - 2)]
	
sieve (p:ns) = p : sieve (filter ((/=0) . (flip mod) p) ns)
primes = sieve [2..]

check = checkPrimes 30 500 500 $ mkStdGen 145

checkPrimes n limit increase gen = let {(randA, gen2) = next gen; rand = randA `mod` limit} in
	do
		putStrLn $ "[" ++ show n ++ "] computing " ++ show rand ++ "th prime."
		let prime = primes !! rand in
			putStrLn $ "result: " ++ show prime
		putStrLn $ take n $ repeat '#'
		if n > 0 then
			checkPrimes (n - 1) (limit + increase) increase gen2
			else return "Done"
	
	
--testTrace = trace "this" 5
testTrace = let n = 10 in 
	trace ("this: " ++ show n) (fibbT n)

-- https://en.wikibooks.org/wiki/Haskell/Debugging
-- https://wiki.haskell.org/Debugging


-- Maybe, fmap

l = [Nothing, Just 2, Nothing, Just 3]

l1 = fmap (fmap (+1)) $ l

l2 = filter (/= Nothing) l

transform l x = case x of
		Nothing -> l
		Just h -> h : l

lp = foldl transform [] l



-- Monad IO

f1 = do l <- getLine; putStrLn l; return (l ++ "a")

f2 = do
		putStr "Enter line 1: "
		l1 <- getLine
		putStrLn $ "Line 1 is: " ++ l1
		putStr "Enter line 2: "
		l2 <- getLine
		putStrLn $ "Line 2 is: " ++ l2
		return (l1 ++ l2)
-- :t f2