[commit: ghc] wip/nfs-locking: Add args -- a variadic version of arg. (6084342)

[git at git.haskell.org]

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

On branch  : wip/nfs-locking
Link       : http://ghc.haskell.org/trac/ghc/changeset/60843423d23b84928c2c1ce2725b5e293cb81061/ghc

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

commit 60843423d23b84928c2c1ce2725b5e293cb81061
Author: Andrey Mokhov <andrey.mokhov at gmail.com>
Date:   Fri Jan 2 03:03:27 2015 +0000

    Add args -- a variadic version of arg.


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

60843423d23b84928c2c1ce2725b5e293cb81061
 src/Base.hs | 16 +++++++++++++++-
 1 file changed, 15 insertions(+), 1 deletion(-)

diff --git a/src/Base.hs b/src/Base.hs
index 77c2858..645d5dc 100644
--- a/src/Base.hs
+++ b/src/Base.hs
@@ -7,7 +7,7 @@ module Base (
     module Data.Monoid,
     module Data.List,
     Stage (..),
-    Args, arg,
+    Args, arg, args, ShowAction (..),
     Condition (..),
     joinArgs, joinArgsWithSpaces, splitArgs,
     filterOut
@@ -38,6 +38,20 @@ instance ShowAction String where
 arg :: ShowAction a => [a] -> Args
 arg = mapM showAction
 
+class Collect a where
+    collect :: Args -> a
+
+instance Collect Args where
+    collect = id
+
+instance (ShowAction a, Collect r) => Collect (a -> r) where
+    collect prev next = collect $ do
+        next' <- showAction next
+        prev <> return [next']
+
+args :: Collect a => a
+args = collect mempty
+
 intercalateArgs :: String -> Args -> Args
 intercalateArgs s args = do
     as <- args