From 8fade4ff288a0925e7e7f4fdb48004d627ede6b6 Mon Sep 17 00:00:00 2001
From: Masahiro Sakai <masahiro.sakai@gmail.com>
Date: Sun, 21 Jun 2015 00:41:01 +0900
Subject: [PATCH] sort literals in a non-linear term when generating OPB/WBO
 files

---
 CHANGELOG.markdown                          | 1 +
 src/Data/PseudoBoolean/Builder.hs           | 4 +++-
 src/Data/PseudoBoolean/ByteStringBuilder.hs | 4 +++-
 3 files changed, 7 insertions(+), 2 deletions(-)

diff --git a/CHANGELOG.markdown b/CHANGELOG.markdown
index 9362df9..cf8a278 100644
--- a/CHANGELOG.markdown
+++ b/CHANGELOG.markdown
@@ -2,3 +2,4 @@
 -------
 * parse* functions fails if the parser does not consume all of the inputs
 * generate '#product=', 'sizeproduct=' and '#soft=' in header line of OPB/WBO files
+* sort literals in a non-linear term when generating OPB/WBO files
diff --git a/src/Data/PseudoBoolean/Builder.hs b/src/Data/PseudoBoolean/Builder.hs
index 3c34827..9adff72 100644
--- a/src/Data/PseudoBoolean/Builder.hs
+++ b/src/Data/PseudoBoolean/Builder.hs
@@ -26,7 +26,9 @@ import Prelude hiding (sum)
 import qualified Data.DList as DList
 import qualified Data.IntSet as IntSet
 import qualified Data.Set as Set
+import Data.List (sortBy)
 import Data.Monoid hiding (Sum (..))
+import Data.Ord
 import Data.String
 import Text.Printf
 import Data.PseudoBoolean.Types
@@ -75,7 +77,7 @@ showWeightedTerm :: (Monoid a, IsString a) => WeightedTerm -> a
 showWeightedTerm (c, lits) = foldr (\f g -> f <> fromString " " <> g) mempty (x:xs)
   where
     x = if c >= 0 then fromString "+" <> fromString (show c) else fromString (show c)
-    xs = map showLit lits
+    xs = map showLit $ sortBy (comparing abs) lits
 
 showLit :: (Monoid a, IsString a) => Lit -> a
 showLit lit = if lit > 0 then v else fromString "~" <> v
diff --git a/src/Data/PseudoBoolean/ByteStringBuilder.hs b/src/Data/PseudoBoolean/ByteStringBuilder.hs
index 6a7e1a0..e466c01 100644
--- a/src/Data/PseudoBoolean/ByteStringBuilder.hs
+++ b/src/Data/PseudoBoolean/ByteStringBuilder.hs
@@ -31,9 +31,11 @@ import qualified Prelude
 import Prelude hiding (sum)
 import qualified Data.IntSet as IntSet
 import qualified Data.Set as Set
+import Data.List (sortBy)
 import Data.Monoid hiding (Sum (..))
 import qualified Data.ByteString.Lazy as BS
 import Data.ByteString.Builder (Builder, intDec, integerDec, char7, string7, hPutBuilder, toLazyByteString)
+import Data.Ord
 import System.IO
 import Data.PseudoBoolean.Types
 
@@ -81,7 +83,7 @@ showWeightedTerm :: WeightedTerm -> Builder
 showWeightedTerm (c, lits) = foldr (\f g -> f <> char7 ' ' <> g) mempty (x:xs)
   where
     x = if c >= 0 then char7 '+' <> integerDec c else integerDec c
-    xs = map showLit lits
+    xs = map showLit $ sortBy (comparing abs) lits
 
 showLit :: Lit -> Builder
 showLit lit = if lit > 0 then v else char7 '~' <> v