From cd9474a9695787666c6aadc333bc272c1e507397 Mon Sep 17 00:00:00 2001
From: Lennart Spitzner <lsp@informatik.uni-kiel.de>
Date: Sat, 6 Aug 2016 19:36:47 +0200
Subject: [PATCH] Change layouting for lambda, app; Fix exponential behaviour

---
 src/Language/Haskell/Brittany/BriLayouter.hs    | 13 +++++++++++--
 src/Language/Haskell/Brittany/Layouters/Expr.hs | 14 +++++++++++---
 2 files changed, 22 insertions(+), 5 deletions(-)

diff --git a/src/Language/Haskell/Brittany/BriLayouter.hs b/src/Language/Haskell/Brittany/BriLayouter.hs
index 976a6ce..88013c4 100644
--- a/src/Language/Haskell/Brittany/BriLayouter.hs
+++ b/src/Language/Haskell/Brittany/BriLayouter.hs
@@ -631,7 +631,15 @@ getSpacings limit bridoc = rec bridoc
               VerticalSpacingParSome i -> i <= colMax
               VerticalSpacingParNonBottom -> True
       let filterAndLimit :: [VerticalSpacing] -> [VerticalSpacing]
-          filterAndLimit = forceList . take limit . filter hasOkColCount
+          filterAndLimit = forceList
+                         . take limit
+                         . filter hasOkColCount
+                         . take (100*limit) -- we need to limit here in case
+                                            -- that the input list is
+                                            -- _large_ with a similarly _large_
+                                            -- prefix not passing hasOkColCount
+                                            -- predicate.
+                                            -- TODO: 100 is arbitrary.
           forceList l = foldl (flip seq) l l
       result <- case brdc of
         -- BDWrapAnnKey _annKey bd -> rec bd
@@ -730,7 +738,8 @@ getSpacings limit bridoc = rec bridoc
           lSpss <- rec `mapM` ls
           let worbled = fmap reverse
                       $ sequence
-                      $ reverse lSpss
+                      $ reverse
+                      $ lSpss
               summed = worbled <&> \lSps@(lSp1:_) ->
                 VerticalSpacing (_vs_sameLine lSp1) 
                                 (spMakePar $ maxVs lSps)
diff --git a/src/Language/Haskell/Brittany/Layouters/Expr.hs b/src/Language/Haskell/Brittany/Layouters/Expr.hs
index 6566756..8873e64 100644
--- a/src/Language/Haskell/Brittany/Layouters/Expr.hs
+++ b/src/Language/Haskell/Brittany/Layouters/Expr.hs
@@ -56,13 +56,15 @@ layoutExpr lexpr@(L _ expr) = docWrapNode lexpr $ case expr of
           docCols ColCasePattern
             $ (patDocs <&> (\p -> docSeq [docForceSingleline p, docSeparator]))
     docAlt
-      [ docSeq
+      [ docSetParSpacing
+      $ docSeq
         [ docLit $ Text.pack "\\"
         , docWrapNode lmatch $ docForceSingleline funcPatternPartLine
         , appSep $ docLit $ Text.pack "->"
         , docWrapNode lgrhs $ docForceParSpacing bodyDoc
         ]
-      , docAddBaseY BrIndentRegular
+      , docSetParSpacing
+      $ docAddBaseY BrIndentRegular
       $ docPar
         (docSeq
           [ docLit $ Text.pack "\\"
@@ -120,6 +122,12 @@ layoutExpr lexpr@(L _ expr) = docWrapNode lexpr $ case expr of
       [ docSeq [appSep $ docForceSingleline expDoc1, docForceSingleline expDoc2]
       , docSetParSpacing
       $ docAddBaseY BrIndentRegular
+      $ docSeq
+        [ appSep $ docForceSingleline expDoc1
+        , docForceParSpacing expDoc2
+        ]
+      , docSetParSpacing
+      $ docAddBaseY BrIndentRegular
       $ docPar
         (docForceSingleline expDoc1)
         expDoc2
@@ -472,7 +480,7 @@ layoutExpr lexpr@(L _ expr) = docWrapNode lexpr $ case expr of
       $ docAddBaseY BrIndentRegular
       $ docPar
           (docLit t)
-          (docLines $ let
+          (docNonBottomSpacing $ docLines $ let
             line1 = docCols ColRecUpdate
               [ appSep $ docLit $ Text.pack "{"
               , appSep $ docLit $ fd1n