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[number] remove gcde_binary

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This commit is contained in:
Vincent Hanquez 2015-05-11 07:10:15 +01:00
parent 5c0daae88c
commit 47afc1720d
1 changed files with 0 additions and 31 deletions
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31
Crypto/Number/Basic.hs
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@ -19,7 +19,6 @@
module Crypto.Number.Basic
( sqrti
, gcde
, gcde_binary
, areEven
, log2
) where
@ -84,36 +83,6 @@ gcde a b = if d < 0 then (-x,-y,-d) else (x,y,d) where
f t (r, sa - (q * sb), ta - (q * tb))
#endif
-- | get the extended GCD of two integer using the extended binary algorithm (HAC 14.61)
-- get (x,y,d) where d = gcd(a,b) and x,y satisfying ax + by = d
gcde_binary :: Integer -> Integer -> (Integer, Integer, Integer)
#if MIN_VERSION_integer_gmp(0,5,1)
gcde_binary = gcde
#else
gcde_binary a' b'
| b' == 0 = (1,0,a')
| a' >= b' = compute a' b'
| otherwise = (\(x,y,d) -> (y,x,d)) $ compute b' a'
where
getEvenMultiplier !g !x !y
| areEven [x,y] = getEvenMultiplier (g `shiftL` 1) (x `shiftR` 1) (y `shiftR` 1)
| otherwise = (x,y,g)
halfLoop !x !y !u !i !j
| areEven [u,i,j] = halfLoop x y (u `shiftR` 1) (i `shiftR` 1) (j `shiftR` 1)
| even u = halfLoop x y (u `shiftR` 1) ((i + y) `shiftR` 1) ((j - x) `shiftR` 1)
| otherwise = (u, i, j)
compute a b =
let (x,y,g) = getEvenMultiplier 1 a b in
loop g x y x y 1 0 0 1
loop g _ _ 0 !v _ _ !c !d = (c, d, g * v)
loop g x y !u !v !a !b !c !d =
let (u2,a2,b2) = halfLoop x y u a b
(v2,c2,d2) = halfLoop x y v c d
in if u2 >= v2
then loop g x y (u2 - v2) v2 (a2 - c2) (b2 - d2) c2 d2
else loop g x y u2 (v2 - u2) a2 b2 (c2 - a2) (d2 - b2)
#endif
-- | check if a list of integer are all even
areEven :: [Integer] -> Bool