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Refactored the equation normalisation and added a custom GCD function

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This commit is contained in:
Neil Brown 2007-12-12 17:40:37 +00:00
parent 94dca6fc10
commit 88f7d1ec92
1 changed files with 8 additions and 7 deletions
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15
transformations/ArrayUsageCheck.hs
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@ -77,13 +77,14 @@ solveConstraints p ineq
normalise = mapM normalise' --Note the mapM; if any calls to normalise' fail, so will normalise
where
normalise' :: EqualityConstraintEquation -> Maybe EqualityConstraintEquation
normalise' e = let g = foldl1 gcd (tail $ elems e) in -- g is the GCD of a_1 .. a_n (not a_0)
if (g == 0)
then Just e
else (if (((e ! 0) `mod` g) /= 0) -- If g doesn't divide a_0
then Nothing
else Just $ amap (\x -> x `div` g) e -- Divide all coefficients by g
)
normalise' e | g == 0 = Just e
| ((e ! 0) `mod` g) /= 0 = Nothing
| otherwise = Just $ amap (\x -> x `div` g) e
where g = foldl1 mygcd (map abs $ tail $ elems e) -- g is the GCD of a_1 .. a_n (not a_0)
mygcd :: Integer -> Integer -> Integer
mygcd 0 0 = 0
mygcd x y = gcd x y
-- | Solves all equality problems in the given list.
-- Will either succeed (Just () in the Error/Maybe monad) or fail (Nothing)