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Today's Topics:
1. Re: about parser question < Programming in haskell _ chapter
8 > (Haisheng Wu)
2. Re: Impossible lib definition? (Christian Maeder)
3. Error in converting the function from let in clause to where
(mukesh tiwari)
----------------------------------------------------------------------
Message: 1
Date: Mon, 18 Jul 2011 19:17:36 +0800
From: Haisheng Wu <[email protected]>
Subject: Re: [Haskell-beginners] about parser question < Programming
in haskell _ chapter 8 >
To: anyzhen <[email protected]>
Cc: Beginners <[email protected]>
Message-ID:
<cafj8lzfrkgnz7gsbj6fbkt_n+q5636ulyq7qe8t98umpnv_...@mail.gmail.com>
Content-Type: text/plain; charset="iso-8859-1"
I think you can check full source code at its web site to see what you
missed.
My thought: did you make Parser as a instance of Monad?
-Haisheng
On Mon, Jul 18, 2011 at 5:20 PM, anyzhen <[email protected]> wrote:
> well,i am reading the book :<*Programming in haskell *>
> *chapter 8* *functional parsers *
> this chapter try teaching an parser technology,but i have some problem
> about *do* keyword
>
> --some brief info of types :
> type Parser a = String -> [(a,String)]
> item :: Parser Char --item "abc" = [('a',"bc")]
> return' :: a -> Parser a --return' 'a' "foo" =
> [('a',"foo")]
>
> --below code complier notice... sorry format
> p2 :: Parser (Char,Char)
> p2 = do x <- item
> item
> y <- item
> return' (x,y)
> *"No instance for (Monad ((-)) String))
> *
> * arising from a execute statement ** ** **
> ** ** *
> * Possible fix : add an instance declaration for **(Monad ((-)) String))**
> *
> *In a stmt of a 'do' expression : y <- item** ** **
> ** ** *
> *In the expression:** ** ** **
> ** ** ** ** *
> * do {** x <- item;** ** ** **
> ** ** ** ** *
> * item;** ** ** ** **
> ** ** ** ** ** *
> * y <- item;** ** ** **
> ** ** ** ** *
> * return' (x,y)}** ** ** **
> ** ** ** *
> * In an equation for 'p2':** ** ** **
> ** ** ** ** *
> * p2 ** ** ** ** **
> ** ** ** ** *
> * = do { ** x <- item;** ** **
> ** ** ** ** *
> * item;** ** ** **
> ** ** ** ** *
> * y <- item;** ** **
> ** ** ** ** *
> * ....**}"** ** **
> ** ** ** ** ** *
> *
> *
> *thanks for any help *
> *jiangzhen <mail:[email protected]>*
>
> _______________________________________________
> Beginners mailing list
> [email protected]
> http://www.haskell.org/mailman/listinfo/beginners
>
>
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Message: 2
Date: Mon, 18 Jul 2011 15:55:55 +0200
From: Christian Maeder <[email protected]>
Subject: Re: [Haskell-beginners] Impossible lib definition?
To: Obscaenvs 74 <[email protected]>
Cc: [email protected]
Message-ID: <[email protected]>
Content-Type: text/plain; charset=ISO-8859-1; format=flowed
Am 18.07.2011 10:27, schrieb Obscaenvs 74:
> From the source of the package Text.ParserCombinators.ReadP, available
> at
> http://hackage.haskell.org/packages/archive/base/latest/doc/html/src/Text-ParserCombinators-ReadP.html#many
> :
>
> many :: ReadP a -> ReadP [a]
> -- ^ Parses zero or more occurrences of the given parser.
> many p = return [] +++ many1 p
>
> many1 :: ReadP a -> ReadP [a]
> -- ^ Parses one or more occurrences of the given parser.
> many1 p = liftM2 (:) p (many p)
>
>
> So `many` is defined in terms of `many1` and vice versa - completely
> understandable, but here the argument (`p`) does not change. This is
> above me right now. Anyone care to explain? I'd be grateful. Not that
> I have to understand it, but it keeps pestering me during my lonely
> hours.
"p" is a common (non-changing) argument for parsing exactly one occurrence.
The termination is controlled by the choice operator +++ or the length
of the input string, provided the argument "p" does consume at least one
character from the input.
HTH Christian
>
> /Fredrik
>
------------------------------
Message: 3
Date: Mon, 18 Jul 2011 20:51:07 +0530
From: mukesh tiwari <[email protected]>
Subject: [Haskell-beginners] Error in converting the function from let
in clause to where
To: [email protected]
Message-ID:
<cafhzve-asd+f+w1gh889ue9q_a4rcs7v9tmv4yycpcfpepv...@mail.gmail.com>
Content-Type: text/plain; charset="iso-8859-1"
Hello all
This is my first post on Haskell-beginner so i am not completely aware of
protocols here . Pardon me for my ignorance . I am trying to implement
elliptic curve prime factorisation and initially wrote
function "addPoints" using let in clause. It works fine. When i converted
the "addPoint" using where clause then its not working and not adding the
points correctly . I run both functions from ghci and
for same point " addPoints ( Conelliptic 1222 34 5678 ) ( Conpoint 123 42567
) ( Conpoint 1234 4322222222222222) " addPoints function using where clause
return Right 2 while let in clause return Left (Conpoint 4840 4122) . Could
some one please help me to find out the bug . In case of indentation problem
, source code on http://hpaste.org/49174 .
Regards
Mukesh Tiwari
--y^2= x^3+ax+b mod n
import Random
import Control.Monad
import Data.List
import Data.Bits
data Elliptic = Conelliptic Integer Integer Integer deriving ( Eq , Show )
data Point = Conpoint Integer Integer | Identity deriving ( Eq , Show )
powM :: Integer -> Integer -> Integer -> Integer
powM a d n
| d == 0 = 1
| d == 1 = mod a n
| otherwise = mod q n where
p = powM ( mod ( a^2 ) n ) ( shiftR d 1 ) n
q = if (.&.) d 1 == 1 then mod ( a * p ) n else p
calSd :: Integer -> IO ( Integer , Integer )
calSd n = return ( s , d ) where
s = until ( \x -> testBit ( n - 1) ( fromIntegral x ) ) ( +1 ) 0
d = div ( n - 1 ) ( shiftL 1 ( fromIntegral s ) )
isProbable::Integer->IO Bool
isProbable n
| n <= 1 = return False
| n == 2 = return True
| even n = return False
| otherwise = calSd n >>= (\( s , d ) -> rabinMiller 0 n s d )
rabinMiller::Integer->Integer->Integer->Integer->IO Bool
rabinMiller cnt n s d
| cnt>=5= return True
| otherwise = randomRIO ( 2 , n - 2 ) >>=
(\a -> case powM a d n == 1 of
True -> rabinMiller ( cnt + 1 ) n s d
_ -> if any ( == pred n ) . take ( fromIntegral s ) .
iterate (\e -> mod ( e^2 ) n ) $ powM a d n then rabinMiller ( cnt + 1) n s
d
else return False )
{--
--add points of elliptic curve
addPoints :: Elliptic -> Point -> Point -> Either Point Integer
addPoints _ Identity p_2 = Left p_2
addPoints _ p_1 Identity = Left p_1
addPoints ( Conelliptic a b n ) ( Conpoint x_p y_p ) ( Conpoint x_q y_q )
| x_p /= x_q = case ( ( Conpoint x_r y_r ) , d ) of
( _ , 1 ) -> Left ( Conpoint x_r y_r )
( _ , d' ) -> Right d'
where
[ u , v , d ] = extended_gcd ( x_p - x_q
) n
s = mod ( ( y_p - y_q ) * u ) n
x_r = mod ( s*s - x_p - x_q ) n
y_r = mod ( -y_p - s * ( x_r - x_p ) ) n
| otherwise = if mod ( y_p + y_q ) n == 0 then Left Identity
else case ( ( Conpoint x_r y_r ) , d ) of
( _ , 1 ) -> Left ( Conpoint x_r y_r )
( _ , d' ) -> Right d'
where
[ u , v , d ] = extended_gcd ( 2 * y_p )
n
s = mod ( ( 3 * x_p * x_p + a ) * u ) n
x_r = mod ( s * s - 2 * x_p ) n
y_r = mod ( -y_p - s * ( x_r - x_p ) ) n
--}
--add points of elliptic curve
addPoints::Elliptic->Point->Point-> Either Point Integer
addPoints _ Identity p_2 = Left p_2
addPoints _ p_1 Identity = Left p_1
addPoints ( Conelliptic a b n ) ( Conpoint x_p y_p ) ( Conpoint x_q y_q )
| x_p /= x_q = let
[ u , v , d ] = extended_gcd (x_p-x_q) n
s = mod ( ( y_p - y_q ) * u ) n
x_r = mod ( s * s - x_p - x_q ) n
y_r= mod ( -y_p - s * ( x_r - x_p ) ) n
in case ( ( Conpoint x_r y_r ) , d ) of
( _ , 1 ) -> Left ( Conpoint x_r y_r )
( _ , d' ) -> Right d'
| otherwise = if mod ( y_p + y_q ) n == 0 then Left Identity
else let
[ u , v , d ] = extended_gcd ( 2*y_p ) n
s = mod ( ( 3 * x_p * x_p + a ) * u ) n
x_r = mod ( s * s - 2 * x_p ) n
y_r = mod ( -y_p - s * ( x_r - x_p ) ) n
in case ( ( Conpoint x_r y_r ) , d ) of
( _ , 1 )-> Left (Conpoint x_r y_r)
( _ , d' ) -> Right d'
extended_gcd::Integer->Integer->[Integer]
extended_gcd u v= helpGcd u v 0 [ [ 1 , 0 ] , [ 0 , 1 ] ] where
helpGcd u v n m @ ( [ [ a , b ] , [ c , d ] ] )
| v == 0 = if u<0 then [ - ( ( -1 ) ^ n ) * ( m !! 1 !! 1 ) , - ( ( -1
) ^ ( n + 1 ) ) * ( m !! 0 !! 1 ) , -u ]
else [ ( ( -1 ) ^ n ) * ( m !! 1 !! 1 ) , ( ( -1 ) ^ (
n + 1 ) ) * ( m !! 0 !! 1 ) , u ]
| otherwise = helpGcd u' v' ( n + 1 ) m' where
( q , v' ) = quotRem u v
t = [ [q , 1 ] , [ 1 , 0 ] ]
m' = [ [ q * a + b , a ] , [ q * c + d , c ] ] --mult m t
u' = v
multiEC :: Elliptic -> Point -> Integer -> IO ( Either Point Integer )
multiEC _ _ 0 = return $ Left Identity
multiEC ecurve point k | k>0 = return $ helpEC Identity point k
where
helpEC p _ 0 = Left p
helpEC p q n =
case (p',q') of
( Left p'' , Left q'' ) -> helpEC p'' q'' (div n 2)
( Right p'' , _ ) -> Right p''
( _ , Right q'' ) -> Right q''
where
p' =if odd n then addPoints ecurve p q else Left p
q' = addPoints ecurve q q
dscrmntEC a b = 4 * a * a * a + 27 * b * b
randomCurve :: Integer -> IO [Integer]
randomCurve n = randomRIO ( 1 , n ) >>= ( \a -> randomRIO ( 1 , n ) >>= ( \u
-> randomRIO (1 , n) >>= (\v -> return [a , mod ( v*v - u*u*u - a*u ) n , n
, u , v ] ) ) )
factor :: Integer -> Integer -> IO [Integer]
factor 1 _ = return []
factor n m =
isProbable n >>= (\x -> if x then return [n]
else
randomCurve n >>= (\[ a , b , n , u , v ] ->
multiEC ( Conelliptic a b n ) ( Conpoint u
v ) m >>=
( \p -> case p of
Left p' -> factor n m
Right p'-> factor ( div n p'
) m >>= ( \x -> factor p' m >>= (\y -> return $ x ++ y ) ) ) ) )
solve :: Integer -> IO [ Integer ]
solve n = factor n ( foldl lcm 1 [1..10000] )
main = liftM read getLine >>=( \n -> solve n ) >>= print
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