Mon Nov 20 20:50:17 UTC 2017

Repository : ssh://git@git.haskell.org/haddock

On branches: 2.17.3.1-spanfix,alexbiehl-patch-1,ghc-8.0,ghc-8.0-facebook,ghc-head,ghc-head1,haddock-quick,headdock-library-1.4.5,ie_avails,issue-303,issue-475,master,pr-filter-maps,pr/cabal-desc,travis,v2.16,v2.17,v2.17.3,v2.18,wip-located-module-as,wip/D2418,wip/T11080-open-data-kinds,wip/T11258,wip/T11430,wip/T12105,wip/T12105-2,wip/T12942,wip/T13163,wip/T3384,wip/embelleshed-rdr,wip/new-tree-one-param,wip/rae,wip/remove-frames,wip/remove-frames1,wip/revert-ttg-2017-11-20,wip/ttg-2017-10-13,wip/ttg-2017-10-31,wip/ttg-2017-11-06,wip/ttg2-2017-11-10,wip/ttg3-2017-11-12,wip/ttg4-constraints-2017-11-13
Link       : http://git.haskell.org/haddock.git/commitdiff/d5700e1427f7171db0e0e9393aedb734b554459f

>---------------------------------------------------------------

commit d5700e1427f7171db0e0e9393aedb734b554459f
Author: Łukasz Hanuszczak <lukasz.hanuszczak at gmail.com>
Date:   Sun Jul 19 18:16:11 2015 +0200

    Add SYB-like utility function for performing stateful queries.


>---------------------------------------------------------------

d5700e1427f7171db0e0e9393aedb734b554459f
 haddock-api/src/Haddock/Syb.hs | 16 +++++++++++++++-
 1 file changed, 15 insertions(+), 1 deletion(-)

diff --git a/haddock-api/src/Haddock/Syb.hs b/haddock-api/src/Haddock/Syb.hs
index 2016b74..4847e48 100644
--- a/haddock-api/src/Haddock/Syb.hs
+++ b/haddock-api/src/Haddock/Syb.hs
@@ -2,7 +2,7 @@
 
 
 module Haddock.Syb
-    ( everything, everywhere
+    ( everything, everythingWithState, everywhere
     , mkT
     , combine
     ) where
@@ -20,6 +20,20 @@ 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)
 
+
+-- | Perform a query with state on each level of a tree.
+--
+-- This is the same as 'everything' but allows for stateful computations. In
+-- SYB it is called @everythingWithContext@ but I find this name somewhat
+-- nicer.
+everythingWithState :: s -> (r -> r -> r)
+                    -> (forall a. Data a => a -> s -> (r, s))
+                    -> (forall a. Data a => a -> r)
+everythingWithState s k f x =
+    let (r, s') = f x s
+    in foldl k r (gmapQ (everythingWithState s' k f) x)
+
+
 -- | Apply transformation on each level of a tree.
 --
 -- Just like 'everything', this is stolen from SYB package.

