From 3814a039d5541d204e4cb52aef45e64cf9f65259 Mon Sep 17 00:00:00 2001
From: Neil Brown <neil@twistedsquare.com>
Date: Fri, 14 Dec 2007 15:17:19 +0000
Subject: [PATCH] Refactored the use of mygcd with foldl into one function

---
 transformations/ArrayUsageCheck.hs    | 6 +++++-
 transformations/RainUsageCheckTest.hs | 2 +-
 2 files changed, 6 insertions(+), 2 deletions(-)

diff --git a/transformations/ArrayUsageCheck.hs b/transformations/ArrayUsageCheck.hs
index 3ea1df7..2e69c01 100644
--- a/transformations/ArrayUsageCheck.hs
+++ b/transformations/ArrayUsageCheck.hs
@@ -86,7 +86,7 @@ solveConstraints p ineq
         normaliseEq' 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)
+                       where g = mygcdList (tail $ elems e) -- g is the GCD of a_1 .. a_n (not a_0)
     
     -- | Solves all equality problems in the given list.
     -- Will either succeed (Just () in the Error/Maybe monad) or fail (Nothing)
@@ -206,6 +206,10 @@ mygcd :: Integer -> Integer -> Integer
 mygcd 0 0 = 0
 mygcd x y = gcd x y
 
+mygcdList :: [Integer] -> Integer
+mygcdList [] = 0
+mygcdList [x] = abs x
+mygcdList (x:xs) = foldl mygcd x xs
 
 -- | Prunes the inequalities.  It does what is described in section 2.3 of Pugh's ACM paper;
 -- it removes redundant inequalities, fails (evaluates to Nothing) if it finds a contradiction
diff --git a/transformations/RainUsageCheckTest.hs b/transformations/RainUsageCheckTest.hs
index b77779a..8619199 100644
--- a/transformations/RainUsageCheckTest.hs
+++ b/transformations/RainUsageCheckTest.hs
@@ -502,7 +502,7 @@ testIndexes = TestList
 -- This is so they can be used as normalised coefficients in a linear equation
 coprimeList :: Int -> Gen [Integer]
 coprimeList size = do non_normal <- replicateM size $ choose (1,100)
-                      return $ map (\x -> x `div` (foldl mygcd 0 non_normal)) non_normal
+                      return $ map (\x -> x `div` (mygcdList non_normal)) non_normal
 
 -- | Generates a list of lists of co-prime numbers, where each list is distinct.
 -- The returned list of lists will be square; N equations, each with N items