[commit: packages/Cabal] ghc-head: Add a comment. (c9a57bc)

[git at git.haskell.org]

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

On branch  : ghc-head
Link       : http://git.haskell.org/?p=packages/Cabal.git;a=commit;h=c9a57bceb98632f15ec2475490626bd9fa9cd331

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

commit c9a57bceb98632f15ec2475490626bd9fa9cd331
Author: Andres Loeh <andres at well-typed.com>
Date:   Fri May 3 14:12:37 2013 +0200

    Add a comment.


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

c9a57bceb98632f15ec2475490626bd9fa9cd331
 cabal-install/Distribution/Client/Dependency/Modular/Log.hs |    4 ++++
 1 file changed, 4 insertions(+)

diff --git a/cabal-install/Distribution/Client/Dependency/Modular/Log.hs b/cabal-install/Distribution/Client/Dependency/Modular/Log.hs
index 3c9216f..3bfe6a9 100644
--- a/cabal-install/Distribution/Client/Dependency/Modular/Log.hs
+++ b/cabal-install/Distribution/Client/Dependency/Modular/Log.hs
@@ -18,6 +18,10 @@ import Distribution.Client.Dependency.Modular.Tree (FailReason(..))
 -- Parameterized over the type of actual messages and the final result.
 type Log m a = Progress m () a
 
+-- | Turns a log into a list of messages paired with a final result. A final result
+-- of 'Nothing' indicates failure. A final result of 'Just' indicates success.
+-- Keep in mind that forcing the second component of the returned pair will force the
+-- entire log.
 runLog :: Log m a -> ([m], Maybe a)
 runLog (Done x)       = ([], Just x)
 runLog (Fail _)       = ([], Nothing)