--- a/src/Tools/Haskell/Haskell.thy Sat Dec 15 16:42:18 2018 +0100
+++ b/src/Tools/Haskell/Haskell.thy Sun Dec 16 12:46:44 2018 +0100
@@ -197,17 +197,19 @@
module Isabelle.Buffer (T, empty, add, content)
where
-newtype T = Buffer [String]
+import Isabelle.Library
+
+
+newtype T = Buffer [Char]
empty :: T
empty = Buffer []
add :: String -> T -> T
-add "" buf = buf
-add x (Buffer xs) = Buffer (x : xs)
+add s (Buffer cs) = Buffer (fold (:) s cs)
content :: T -> String
-content (Buffer xs) = concat (reverse xs)
+content (Buffer cs) = reverse cs
\<close>
generate_file "Isabelle/Properties.hs" = \<open>