fixed

commit 4c5b8fa72b0c8044a1b78a01de68b47ff930dbac
parent bbe5cf300c2e9ad9238cab2ab243a081f8923bc9
Author: Jared Tobin <jared@jtobin.io>
Date:   Fri, 12 Dec 2025 16:29:37 +0400

lib: add 'odd' for wider and montgomery

Diffstat:
M
lib/Data/Word/Wider.hs
 | 
21
++++++++++++++++++++-
M
lib/Numeric/Montgomery/Secp256k1/Curve.hs
 | 
20
+++++++++++++++++++-
M
lib/Numeric/Montgomery/Secp256k1/Scalar.hs
 | 
18
++++++++++++++++++

3 files changed, 57 insertions(+), 2 deletions(-)
diff --git a/lib/Data/Word/Wider.hs b/lib/Data/Word/Wider.hs
@@ -29,6 +29,10 @@ module Data.Word.Wider (
   , gt#
   , cmp#
 
+  -- * Parity
+  , odd#
+  , odd
+
   -- * Constant-time selection
   , select
   , select#
@@ -79,7 +83,7 @@ import Data.Word.Limb (Limb(..))
 import qualified Data.Word.Limb as L
 import GHC.Exts (Word(..), Int(..), Int#)
 import qualified GHC.Exts as Exts
-import Prelude hiding (div, mod, or, and, not, quot, rem, recip)
+import Prelude hiding (div, mod, or, and, not, quot, rem, recip, odd)
 
 -- utilities ------------------------------------------------------------------
 
@@ -728,3 +732,18 @@ sqr (Wider w) =
   let !(# l, h #) = sqr# w
   in  (Wider l, Wider h)
 
+odd# :: (# Limb, Limb, Limb, Limb #) -> C.Choice
+odd# (# Limb w, _, _, _ #) = C.from_word_lsb# (Exts.and# w 1##)
+{-# INLINE odd# #-}
+
+-- | Check if a 'Wider' is odd.
+--
+--   >>> odd 1
+--   True
+--   >>> odd 2
+--   False
+odd
+  :: Wider
+  -> Bool
+odd (Wider w) = C.decide (odd# w)
+
diff --git a/lib/Numeric/Montgomery/Secp256k1/Curve.hs b/lib/Numeric/Montgomery/Secp256k1/Curve.hs
@@ -49,6 +49,8 @@ module Numeric.Montgomery.Secp256k1.Curve (
   , inv#
   , sqrt
   , exp
+  , odd#
+  , odd
   ) where
 
 import Control.DeepSeq
@@ -60,7 +62,7 @@ import qualified Data.Word.Wide as W
 import Data.Word.Wider (Wider(..))
 import qualified Data.Word.Wider as WW
 import GHC.Exts (Word(..))
-import Prelude hiding (div, mod, or, and, not, quot, rem, recip, sqrt, exp)
+import Prelude hiding (or, and, not, sqrt, exp, odd)
 
 -- montgomery arithmetic, specialized to the secp256k1 field prime modulus
 -- 0xFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFEFFFFFC2F
@@ -998,6 +1000,8 @@ sqrt n =
       then Just $! rv
       else Nothing
 
+-- XX want unboxed variants
+
 -- | Exponentiation in the Montgomery domain.
 --
 --   >>> exp 2 3
@@ -1014,3 +1018,17 @@ exp b = loop 1 b where
               | otherwise = r
       in  loop nr nm ne
     _ -> r
+
+odd# :: (# Limb, Limb, Limb, Limb #) -> C.Choice
+odd# = WW.odd#
+
+-- | Check if a 'Montgomery' value is odd.
+--
+--   >>> odd 1
+--   True
+--   >>> odd 2
+--   False
+--   >>> Data.Word.Wider.odd (retr 3) -- parity is preserved
+--   True
+odd :: Montgomery -> Bool
+odd (Montgomery m) = C.decide (odd# m)
diff --git a/lib/Numeric/Montgomery/Secp256k1/Scalar.hs b/lib/Numeric/Montgomery/Secp256k1/Scalar.hs
@@ -48,6 +48,8 @@ module Numeric.Montgomery.Secp256k1.Scalar (
   , inv
   , inv#
   , exp
+  , odd#
+  , odd
   ) where
 
 import Control.DeepSeq
@@ -936,6 +938,8 @@ inv
   -> Montgomery -- ^ inverse
 inv (Montgomery w) = Montgomery (inv# w)
 
+-- XX want unboxed variant
+
 -- | Exponentiation in the Montgomery domain.
 --
 --   >>> exp 2 3
@@ -952,3 +956,17 @@ exp b = loop 1 b where
               | otherwise = r
       in  loop nr nm ne
     _ -> r
+
+odd# :: (# Limb, Limb, Limb, Limb #) -> C.Choice
+odd# = WW.odd#
+
+-- | Check if a 'Montgomery' value is odd.
+--
+--   >>> odd 1
+--   True
+--   >>> odd 2
+--   False
+--   >>> Data.Word.Wider.odd (retr 3) -- parity is preserved
+--   True
+odd :: Montgomery -> Bool
+odd (Montgomery m) = C.decide (odd# m)