Move SYB utilities to standalone module.

1 files changed, 26 insertions, 0 deletions

diff --git a/haddock-api/src/Haddock/Syb.hs b/haddock-api/src/Haddock/Syb.hs
new file mode 100644
index 00000000..dd7ffc1b
--- /dev/null
+++ b/haddock-api/src/Haddock/Syb.hs
@@ -0,0 +1,26 @@
+{-# LANGUAGE Rank2Types #-}
+
+
+module Haddock.Syb
+    ( everything
+    , combine
+    ) where
+
+
+import Data.Data
+import Control.Applicative
+
+
+-- | Perform a query on each level of a tree.
+--
+-- This is stolen directly from SYB package and copied here to not introduce
+-- additional dependencies.
+everything :: (r -> r -> r) -> (forall a. Data a => a -> r)
+           -> (forall a. Data a => a -> r)
+everything k f x = foldl k (f x) (gmapQ (everything k f) x)
+
+-- | Combine two queries into one using alternative combinator.
+combine :: Alternative f => (forall a. Data a => a -> f r)
+                         -> (forall a. Data a => a -> f r)
+                         -> (forall a. Data a => a -> f r)
+combine f g x = f x <|> g x