[project @ 1996-01-11 14:06:51 by partain]

[ghc-hetmet.git] / ghc / lib / prelude / List.hs

diff --git a/ghc/lib/prelude/List.hs b/ghc/lib/prelude/List.hs
index 6059ee8..9ef43b6 100644 (file)
--- a/ghc/lib/prelude/List.hs
+++ b/ghc/lib/prelude/List.hs
@@ -665,9 +665,9 @@ concat                      =  foldr (++) []
 # ifndef USE_FOLDR_BUILD
 -- HBC version (stolen)
 concat []              = []
-concat ([]:xss)                = concat xss                    -- for better stack behaiour!
-concat ([x]:xss)       = x : concat xss                -- this should help too ???
-concat (xs:xss)                = xs ++ concat xss
+concat ([]:xss)                = concat xss                    -- for better stack behaviour!
+--NO:bad strictness: concat ([x]:xss)  = x : concat xss -- this should help too ???
+concat ((y:ys):xss)     = y : (ys ++ concat xss)
 # else
 {-# INLINE concat #-}
 concat xs = _build (\ c n -> foldr (\ x y -> foldr c y x) n xs)