1 files changed, 27 insertions, 11 deletions

diff --git a/lib/CommandLine.hs b/lib/CommandLine.hs
index ea5d6b8..2676260 100644
--- a/lib/CommandLine.hs
+++ b/lib/CommandLine.hs
@@ -14,6 +14,8 @@ module CommandLine
     , fancy
     , runArgs
     , arg
+    , args
+    , flag
     , param
     , params
     , label
@@ -50,11 +52,11 @@ type MergeData = [(Int,Ordering)]
 data Expr a where
     --  Prim
     --
-    --   Takes a function from the option arguments and unamed arguments repsectively to
-    --   a value of type a, usually IO (), and gives you an expression tree. As one
-    --   traverses down the tree only the 'interesting' option arguments are passed
-    --   to this function, but all of the unnamed arguments are passed regardless of
-    --   where we are in the tree.
+    --   Takes a function from the option arguments and unnamed arguments
+    --   respectively to a value of type a, usually IO (), and gives you an
+    --   expression tree. As one traverses down the tree only the 'interesting'
+    --   option arguments are passed to this function, but all of the unnamed
+    --   arguments are passed regardless of where we are in the tree.
     --
     Prim :: ([[String]] -> [String] -> a) -> Interval (SuperOrd Int) -> Expr a
     --  Star
@@ -233,17 +235,31 @@ mergeBy comp xs ys = trace (unlines ["xs="++show xs,"ys="++show ys,"mergeData="+
 -}
 
 
+-- | The nth unnamed argument.
 param :: Int -> Args String
 param n = Args (Prim (\_ us -> us!!n) (singleton $ exactly (n+1))) []
 
+-- | All unnamed arguments as a list.
+params :: Args [String]
+params = Args (Prim (\_ args -> args) (exactly 0 ... PositiveInfinity)) []
+
+
+-- | The value of named by the given option name.
 arg :: String -> Args String
 arg optname = Args (Prim (\opts _ -> concat $ take 1 $ concat $ take 1 opts)
-                   (singleton $ exactly 0))
+                         (singleton $ exactly 0))
                    [optname]
 
-params :: Args [String]
-params = Args (Prim (\_ args -> args) (exactly 0 ... PositiveInfinity)) []
+-- | All values named by the given option name.
+args :: String -> Args [String]
+args optname = fromMaybe [] <$> optional
+                (Args (Prim (\opts _ -> concat $ take 1 opts)
+                            (singleton $ exactly 0)) -- no unnamed arguments
+                      [optname])                     -- one named argument
 
+-- | True if the given named option is present.
+flag :: String -> Args Bool
+flag optname = maybe False (const True) <$> optional (arg optname)
 
 label :: String -> Args a -> Args a
 label _ = id
@@ -286,7 +302,7 @@ vanilla flags  = ArgsStyle { parseInvocation = parse flags }
 --
 --   * default polyvariadic - Implicit polyvariadic option if no other option is specified.
 --
-fancy :: [([Char], Int)] -> [[Char]] -> [Char] -> ArgsStyle
+fancy :: [(String, Int)] -> [String] -> String -> ArgsStyle
 fancy sargspsec polyVariadicArgs defaultPoly = ArgsStyle
     { parseInvocation = parse sargspsec polyVariadicArgs defaultPoly }
  where
@@ -470,8 +486,8 @@ runArgs (os,us) c
  where
     os' = sortOn fst os
     dups = mapMaybe notSingle $ groupBy ((==) `on` fst) (os' :: [(String,[String])])
-        where notSingle [x] = Nothing
-              notSingle ((k,v):xs)  = Just (k,v : map snd xs)
+        where notSingle [x]        = Nothing
+              notSingle ((k,v):xs) = Just (k,v : map snd xs)
     getbit = Map.fromList $ zip (accepts c) [0..]
     goods :: [(Int,[String])]
     (bads,goods) = partitionEithers $ map f os'