1 files changed, 39 insertions, 0 deletions
diff --git a/testsuite/tests/simplCore/prog002/Simpl009Help.hs b/testsuite/tests/simplCore/prog002/Simpl009Help.hs
new file mode 100644
index 0000000000..ac75943016
--- /dev/null
+++ b/testsuite/tests/simplCore/prog002/Simpl009Help.hs
@@ -0,0 +1,39 @@
+{-# LANGUAGE ScopedTypeVariables, RankNTypes #-}
+
+-- Helper for simpl009.hs (see comments there)
+
+module Simpl009Help where
+  
+import Control.Monad
+
+newtype Parser s a
+  = Parser (forall res . (a -> [String] -> P s res) -> [String] -> P s res)
+
+data P s res
+  = Symbol (s -> P s res)
+  | Fail [String] [String]
+  | Result res (P s res)
+
+instance Monad (Parser s) where
+  return a = Parser (\fut -> fut a)
+  
+  Parser f >>= k =
+    Parser (\fut -> f (\a -> let Parser g = k a in g fut))
+
+  fail s =
+    Parser (\fut exp -> Fail exp [s])
+
+instance MonadPlus (Parser s) where
+  mplus = error "urk"
+  mzero = Parser (\fut exp -> Fail exp [])
+
+lookAhead :: forall s. Parser s s
+lookAhead =
+  Parser (\fut exp -> Symbol (\c ->
+    feed c (fut c [])
+  ))
+ where
+  feed :: forall res. s -> P s res -> P s res
+  feed c (Symbol sym)     = sym c
+  feed c (Result res fut) = Result res (feed c fut)
+  feed c p@(Fail _ _)     = p