diff --git a/README.md b/README.md
--- a/README.md
+++ b/README.md
@@ -1,4 +1,4 @@
-CmdTheLine v0.2.1.1
+CmdTheLine v0.2.1
 ===============
 
 [![Build Status](https://secure.travis-ci.org/eli-frey/cmdtheline.png)](http://travis-ci.org/eli-frey/cmdtheline)
@@ -39,6 +39,11 @@
 
 ###0.3
 The next release candidate.
+
+Contributors
+------------
+
+Bas Van Dijk -- GetOpt adapter
 
 LICENSE
 -------
diff --git a/cmdtheline.cabal b/cmdtheline.cabal
--- a/cmdtheline.cabal
+++ b/cmdtheline.cabal
@@ -1,5 +1,5 @@
 Name: cmdtheline
-Version: 0.2.1.1
+Version: 0.2.2
 Synopsis: Declarative command-line option parsing and documentation library.
 Description:
   CmdTheLine aims to remove tedium from the definition of command-line
@@ -41,6 +41,11 @@
     now two new functions exported with System.Console.CmdTheLine.Term, 'unwrap'
     and 'unwrapChoice'.  As well a datatype representing cause of early exit,
     'EvalExit' is exported.
+  .
+  Changes since 0.2.1
+  .
+  * Added adapter for interfacing with Getopt in module
+    'System.Console.CmdTheLine'.
 
 Homepage:      http://github.com/eli-frey/cmdtheline
 License:       MIT
@@ -64,13 +69,14 @@
   build-depends:  base >= 4.5 && < 5, containers >= 0.4 && < 0.6,
                   parsec >= 3.1 && < 3.2, pretty >= 1.1 && < 1.2,
                   process >= 1.1, directory >= 1.1,
-                  transformers >= 0.3 && < 0.4, filepath >= 1.3 && < 1.4
+                  transformers >= 0.2 && < 0.4, filepath >= 1.3 && < 1.4
 
   exposed-modules: System.Console.CmdTheLine,
                    System.Console.CmdTheLine.Arg,
                    System.Console.CmdTheLine.ArgVal,
                    System.Console.CmdTheLine.Term,
                    System.Console.CmdTheLine.Util
+                   System.Console.CmdTheLine.GetOpt
 
   other-modules:   System.Console.CmdTheLine.Common,
                    System.Console.CmdTheLine.Err,
@@ -82,12 +88,12 @@
 test-suite Main
   type:          exitcode-stdio-1.0
   build-depends: base >= 4 && < 5, HUnit  >= 1.2.4 && < 2,
-                 test-framework >= 0.6 && < 0.7,
-                 test-framework-hunit >= 0.2 && < 0.3,
+                 test-framework >= 0.6 && < 0.9,
+                 test-framework-hunit >= 0.2 && < 0.4,
                  containers >= 0.4 && < 0.6,
                  parsec >= 3.1 && < 3.2, pretty >= 1.1 && < 1.2,
                  process >= 1.1, directory >= 1.1,
-                 transformers >= 0.3 && < 0.4, filepath >= 1.3 && < 1.4
-  ghc-options:   -Wall -rtsopts
+                 transformers >= 0.2 && < 0.4, filepath >= 1.3 && < 1.4
+  ghc-options:   -Wall -Werror -fno-warn-name-shadowing -rtsopts
   hs-source-dirs: src, test
   main-is:        Main.hs
diff --git a/src/System/Console/CmdTheLine.hs b/src/System/Console/CmdTheLine.hs
--- a/src/System/Console/CmdTheLine.hs
+++ b/src/System/Console/CmdTheLine.hs
@@ -32,11 +32,6 @@
 import System.Console.CmdTheLine.Err
 import System.Console.CmdTheLine.Util
 
-import Text.PrettyPrint ( Doc )
-
-import Control.Monad    ( join )
-import Control.Monad.Trans.Error ( throwError )
-
 {-$term
 
   CmdTheLine is centered around the 'Term' Applicative Functor.  It allows us
diff --git a/src/System/Console/CmdTheLine/Arg.hs b/src/System/Console/CmdTheLine/Arg.hs
--- a/src/System/Console/CmdTheLine/Arg.hs
+++ b/src/System/Console/CmdTheLine/Arg.hs
@@ -29,7 +29,6 @@
 import System.Console.CmdTheLine.CmdLine ( optArg, posArg )
 import System.Console.CmdTheLine.ArgVal  ( ArgVal, pp, parser )
 import qualified System.Console.CmdTheLine.Err  as E
-import qualified System.Console.CmdTheLine.Trie as T
 
 import Control.Applicative
 import Control.Arrow       ( second )
@@ -38,7 +37,7 @@
 
 import Text.PrettyPrint
 
-import Data.List     ( sort, sortBy )
+import Data.List     ( sortBy, foldl' )
 import Data.Function ( on )
 
 argFail :: Doc -> Err a
@@ -53,7 +52,7 @@
 --
 -- [@optDoc@]  :: String: defaults to @\"\"@.
 --
--- [@otpSec@]  :: String: defautts to @\"OPTIONS\"@.
+-- [@optSec@]  :: String: defaults to @\"OPTIONS\"@.
 data OptInfo = OInf
   { unOInf  :: ArgInfo
   , optName :: String
@@ -122,6 +121,7 @@
 --
 -- It is considered a programming error to provide an empty list of names to
 -- optInfo.
+optInfo :: [String] -> OptInfo
 optInfo [] =
   error "System.Console.CmdTheLine.Arg.optInfo recieved empty list of names."
 optInfo names = OInf (mkInfo names) "" "" "OPTIONS"
@@ -248,7 +248,7 @@
     | otherwise = ai { repeatable = True }
 
   yield _ cl = do
-    result <- foldl addLookup (return []) assoc'
+    result <- foldl' addLookup (return []) assoc'
     case result of
       [] -> return vs
       _  -> return . map snd $ sortBy (compare `on` fst) result
@@ -422,6 +422,7 @@
 -- Arguments as terms.
 --
 
+absent :: [ArgInfo] -> [ArgInfo]
 absent = map (\ ai -> ai { absence = Absent })
 
 -- | 'value' @arg@ makes @arg@ into a 'Term'.
diff --git a/src/System/Console/CmdTheLine/ArgVal.hs b/src/System/Console/CmdTheLine/ArgVal.hs
--- a/src/System/Console/CmdTheLine/ArgVal.hs
+++ b/src/System/Console/CmdTheLine/ArgVal.hs
@@ -19,13 +19,13 @@
   , pair, triple, quadruple, quintuple
   ) where
 
-import System.Console.CmdTheLine.Common ( splitOn, select )
+import System.Console.CmdTheLine.Common ( splitOn, select, HelpFormat(..) )
 import qualified System.Console.CmdTheLine.Err as E
 import qualified System.Console.CmdTheLine.Trie as T
 
 import Control.Arrow ( first, (***) )
 import Data.Function ( on )
-import Data.List     ( sort, unfoldr )
+import Data.List     ( sort, unfoldr, foldl' )
 import Data.Ratio    ( Ratio )
 import Data.Tuple    ( swap )
 
@@ -55,11 +55,14 @@
 pp     :: ArgVal a => ArgPrinter a
 pp = snd converter
 
+decPoint, digits, sign :: Parsec String () String
 decPoint      = string "."
 digits        = many1 digit
-concatParsers = foldl (liftA2 (++)) $ return []
 sign          = option "" $ string "-"
 
+concatParsers :: [Parsec String () String] -> Parsec String () String
+concatParsers = foldl' (liftA2 (++)) $ return []
+
 pInteger  :: ( Read a, Integral a ) => Parsec String () a
 pFloating :: ( Read a, Floating a ) => Parsec String () a
 pInteger      = read <$> concatParsers [ sign, digits ]
@@ -224,6 +227,7 @@
     split []  = Nothing
     split str = Just $ splitOn sep str
 
+invalidVal :: String -> String -> Doc
 invalidVal = E.invalidVal `on` text
 
 instance ArgVal Bool where
@@ -292,4 +296,13 @@
         invalidVal str "expected a ratio in the form '<numerator> % <denominator>'"
 
 instance ArgVal (Maybe (Ratio Integer)) where
+  converter = just
+
+instance ArgVal HelpFormat where
+  converter = enum [ ( "pager", Pager )
+                   , ( "plain", Plain )
+                   , ( "groff", Groff )
+                   ]
+
+instance ArgVal (Maybe HelpFormat) where
   converter = just
diff --git a/src/System/Console/CmdTheLine/CmdLine.hs b/src/System/Console/CmdTheLine/CmdLine.hs
--- a/src/System/Console/CmdTheLine/CmdLine.hs
+++ b/src/System/Console/CmdTheLine/CmdLine.hs
@@ -19,9 +19,7 @@
 import qualified System.Console.CmdTheLine.Trie as T
 import qualified Data.Map as M
 
-import Data.List     ( sort )
-import Data.Function ( on )
-
+import Data.List ( sort, foldl' )
 
 optArg :: CmdLine -> ArgInfo -> [( Int, String, Maybe String )]
 optArg cl ai = case M.lookup ai cl of
@@ -42,19 +40,19 @@
  - ArgInfo to an empty list of Arg.
  -}
 argInfoIndexes :: [ArgInfo] -> ( T.Trie ArgInfo, [ArgInfo], CmdLine )
-argInfoIndexes = foldl go ( T.empty, [], M.empty )
+argInfoIndexes = foldl' go ( T.empty, [], M.empty )
   where
   go ( optTrie, posAis, cl ) ai
     | isPos ai  = ( optTrie
                   , ai : posAis
                   , M.insert ai (Pos []) cl
                   )
-    | otherwise = ( foldl add optTrie $ optNames ai
+    | otherwise = ( foldl' add optTrie $ optNames ai
                   , posAis
                   , M.insert ai (Opt []) cl
                   )
     where
-    add t name = T.add t name ai
+    add t name = T.add name ai t
 
 parseOptArg :: String -> ( String, Maybe String )
 parseOptArg str
@@ -133,7 +131,7 @@
   last   = length args - 1
   excess = E.posExcess . map text $ takeEnd (last - maxSpec) args
 
-  ( cl', maxSpec ) = foldl go ( cl, -1 ) posInfo
+  ( cl', maxSpec ) = foldl' go ( cl, -1 ) posInfo
 
   takeEnd n = reverse . take n . reverse
 
diff --git a/src/System/Console/CmdTheLine/Common.hs b/src/System/Console/CmdTheLine/Common.hs
--- a/src/System/Console/CmdTheLine/Common.hs
+++ b/src/System/Console/CmdTheLine/Common.hs
@@ -6,6 +6,7 @@
 
 import Data.Function    ( on )
 import Text.PrettyPrint ( Doc, text )
+import Control.Applicative ( Applicative(..) )
 
 import qualified Data.Map as M
 
@@ -129,6 +130,7 @@
   } deriving ( Eq )
 
 -- | A default 'TermInfo'.
+defTI :: TermInfo
 defTI = TermInfo
   { termName  = ""
   , version   = ""
@@ -167,7 +169,20 @@
 -- in the context of being computed from the command line arguments.
 data Term a = Term [ArgInfo] (Yield a)
 
+instance Functor Term where
+  fmap = yield . result . result . fmap
+    where
+    yield f (Term ais y) = Term ais (f y)
+    result = (.)
 
+instance Applicative Term where
+  pure v = Term [] (\ _ _ -> return v)
+
+  (Term args f) <*> (Term args' v) = Term (args ++ args') wrapped
+    where
+    wrapped ei cl = f ei cl <*> v ei cl
+
+
 data EvalKind = Simple   -- The program has no commands.
               | Main     -- The default program is running.
               | Choice   -- A command has been chosen.
@@ -181,6 +196,7 @@
 descCompare :: Ord a => a -> a -> Ordering
 descCompare = flip compare
 
+splitOn :: Eq a => a -> [a] -> ( [a], [a] )
 splitOn sep xs = ( left, rest' )
   where
   rest' = if rest == [] then rest else tail rest -- Skip the 'sep'.
diff --git a/src/System/Console/CmdTheLine/Err.hs b/src/System/Console/CmdTheLine/Err.hs
--- a/src/System/Console/CmdTheLine/Err.hs
+++ b/src/System/Console/CmdTheLine/Err.hs
@@ -8,7 +8,6 @@
 import qualified System.Console.CmdTheLine.Help as H
 
 import Text.PrettyPrint
-import Data.List ( intersperse )
 
 import Control.Monad ( join )
 import Control.Monad.Trans.Error
@@ -40,52 +39,74 @@
 hsepMap :: (a -> Doc) -> [a] -> Doc
 hsepMap f = hsep . map f
 
-errArgv     = text "argv array must have at least one element"
+errArgv :: Doc
+errArgv = text "argv array must have at least one element"
+
+errNotOpt, errNotPos :: String
 errNotOpt   = "Option argument without name"
 errNotPos   = "Positional argument with a name"
+
+errHelp :: Doc -> Doc
 errHelp doc = text "term error, help requested for unknown command" <+> doc
 
 
+alts :: [String] -> Doc
 alts []    = error "alts called on empty list"
-alts [x]   = error "alts called on singleton list"
+alts [_]   = error "alts called on singleton list"
 alts [x,y] = hsepMap text [ "either", x, "or", y ]
 alts xs    = text "one of:" <+> fsep (punctuate (char ',') (map text xs))
 
+invalid :: String -> Doc -> Doc -> Doc
 invalid kind s exp = hsep
   [ text "invalid", text kind, quotes s<>char ',', exp ]
 
+invalidVal :: Doc -> Doc -> Doc
 invalidVal = invalid "value"
 
+no :: String -> String -> Doc
 no kind s = sep [ text "no such", text kind, quotes $ text s ]
 
+notDir :: Doc -> Doc
 notDir  s = quotes (s) <+> text "is not a directory"
 
+isDir :: Doc -> Doc
 isDir   s = quotes (s) <+> text "is a directory"
 
+element :: String -> String -> Doc -> Doc
 element kind str exp = fsep
   [ text "invalid element in", text kind, parens . quotes $ text str, exp ]
 
+sepMiss :: Char -> String -> Doc
 sepMiss sep str = invalidVal (text str) $
   hsep [ text "missing a", quotes $ char sep, text "separator" ]
 
+unknown :: String -> String -> Doc
 unknown kind v = sep [ text "unknown", text kind, quotes $ text v ]
 
+ambiguous :: String -> String -> [String] -> Doc
 ambiguous kind s ambs = hsep
   [ text kind, quotes $ text s, text "ambiguous, could be", alts ambs ]
 
+posExcess :: [Doc] -> Doc
 posExcess excess = text "too many arguments, don't know what to do with"
                <+> hsepMap prep excess
   where
   prep = (<> text ",") . quotes
 
+flagValue :: String -> String -> Doc
 flagValue f v = hsep
   [ text "option", quotes $ text f
   , text "is a flag, it cannot take the argument", quotes $ text v
   ]
 
+optValueMissing :: String -> Doc
 optValueMissing f = hsep
   [ text "option", quotes $ text f, text "needs an argument" ]
+
+optParseValue :: String -> Doc -> Doc
 optParseValue f e = sep [ text "option" <+> (quotes (text f)<>char ':'), e ]
+
+optRepeated :: String -> String -> Doc
 optRepeated f f'
   | f == f' = hsep
     [ text "option", quotes $ text f, text "cannot be repeated" ]
@@ -117,6 +138,7 @@
     longName (x : xs)
       | length x > 2 || xs == [] = x
       | otherwise                = longName xs
+    longName [] = undefined
 
 print :: Handle -> EvalInfo -> Doc -> IO ()
 print h ei e = hPrint h $ (text . termName . fst $ main ei) <> char ':' <+> e
diff --git a/src/System/Console/CmdTheLine/GetOpt.hs b/src/System/Console/CmdTheLine/GetOpt.hs
new file mode 100644
--- /dev/null
+++ b/src/System/Console/CmdTheLine/GetOpt.hs
@@ -0,0 +1,34 @@
+-- | Adapter for "System.Console.GetOpt".
+module System.Console.CmdTheLine.GetOpt where
+
+import Data.Maybe
+import Data.Traversable
+import System.Console.GetOpt
+import System.Console.CmdTheLine
+
+-- | Sequence a list of @'OptDescr's@ into a term. Absent flags
+-- (specified with 'NoArg') are filtered out.
+optDescrsTerm :: [OptDescr a] -> Term [a]
+optDescrsTerm = fmap catMaybes . sequenceA . map optDescrToTerm
+
+-- | Convert an 'OptDescr' into a 'Term' which returns 'Nothing' if
+-- 'NoArg' is specified and the flag is absent or 'Just' the argument
+-- otherwise.
+optDescrToTerm :: OptDescr a -> Term (Maybe a)
+optDescrToTerm (Option shorts longs argDescr descr) =
+    case argDescr of
+      NoArg x        -> fmap (optional x) $ value $ flag                       $ optInf ""
+      ReqArg to name -> fmap (fmap   to)  $ value $ opt                Nothing $ optInf name
+      OptArg to name -> fmap (Just . to)  $ value $ defaultOpt Nothing Nothing $ optInf name
+    where
+      optional :: a -> Bool -> Maybe a
+      optional x present | present   = Just x
+                         | otherwise = Nothing
+
+      optInf :: String -> OptInfo
+      optInf name = (optInfo options) { optDoc  = descr
+                                      , optName = name
+                                      }
+
+      options :: [String]
+      options = map (:[]) shorts ++ longs
diff --git a/src/System/Console/CmdTheLine/Help.hs b/src/System/Console/CmdTheLine/Help.hs
--- a/src/System/Console/CmdTheLine/Help.hs
+++ b/src/System/Console/CmdTheLine/Help.hs
@@ -2,20 +2,22 @@
  - This is open source software distributed under a MIT license.
  - See the file 'LICENSE' for further information.
  -}
-module System.Console.CmdTheLine.Help where
+module System.Console.CmdTheLine.Help
+  ( printVersion, invocation, prepSynopsis, print ) where
 
+import Prelude hiding ( print )
+
 import System.Console.CmdTheLine.Common
 import qualified System.Console.CmdTheLine.Manpage as Man
 
 import Control.Applicative
-import Control.Arrow       ( first, second )
+import Control.Arrow       ( first )
 
 import Data.Char     ( toUpper, toLower )
-import Data.List     ( intersperse, sort, sortBy, partition )
+import Data.List     ( intersperse, sort, sortBy, partition, foldl' )
 import Data.Function ( on )
-import Data.Maybe    ( catMaybes )
 
-import System.IO
+import System.IO hiding ( print )
 
 
 invocation :: Char -> EvalInfo -> String
@@ -60,7 +62,7 @@
   where
   args = concat . intersperse " " $ map snd args'
     where
-    args' = sortBy revCmp . foldl formatPos [] . snd $ term ei
+    args' = sortBy compare' . foldl' formatPos [] . snd $ term ei
 
   formatPos acc ai
     | isOpt ai  = acc
@@ -78,38 +80,40 @@
       PosN _ _ -> ""
       _        -> "..."
 
-  revCmp ( p, _ ) ( p', _ ) = case ( p', p ) of
-    ( _,             PosAny    ) -> LT
-    ( PosAny,        _         ) -> GT
-    ( PosL  _     _, PosR  _ _ ) -> LT
-    ( PosR  _     _, PosL  _ _ ) -> GT
-    ( p, p' ) -> bifurcate
+  compare' ( p, _ ) ( p', _ ) = case ( p', p ) of
+    ( _,          PosAny    ) -> LT
+    ( PosAny,     _         ) -> GT
+    ( PosL  _  _, PosR  _ _ ) -> LT
+    ( PosR  _  _, PosL  _ _ ) -> GT
+    _ -> comparePos k k'
     where
-    bifurcate
-      | not (getBool p) && not (getBool p') = case ( p, p' ) of
-        ( PosL _ _,  PosN _ _ ) -> if k <= k' then LT else GT
-        ( PosN _ _,  PosL _ _ ) -> if k >= k' then GT else LT
-        ( PosN _ _,  _        ) -> if k <= k' then LT else GT
-        _                       -> if k >= k' then GT else LT
-
+    comparePos
       | getBool p && getBool p' = case ( p, p' ) of
-        ( PosL _ _,  PosN _ _ ) -> if k >= k' then LT else GT
-        ( PosN _ _,  PosL _ _ ) -> if k <= k' then GT else LT
-        ( PosN _ _,  _        ) -> if k >= k' then LT else GT
-        _                       -> if k <= k' then GT else LT
-      where
-      k  = getPos p
-      k' = getPos p'
+        ( PosL _ _, PosN _ _ ) -> flip compare -- if k >= k' then LT else GT
+        ( PosN _ _, PosL _ _ ) -> compare -- if k <= k' then GT else LT
+        ( PosN _ _, _        ) -> flip compare -- if k >= k' then LT else GT
+        _                      -> compare -- if k <= k' then GT else LT
 
+      | otherwise = case ( p, p' ) of
+        ( PosL _ _, PosN _ _ ) -> compare -- if k <= k' then LT else GT
+        ( PosN _ _, PosL _ _ ) -> flip compare -- if k >= k' then GT else LT
+        ( PosN _ _, _        ) -> compare -- if k <= k' then LT else GT
+        _                      -> flip compare -- if k >= k' then GT else LT
+
+    k  = getPos p
+    k' = getPos p'
+
     getPos x = case x of
       PosL  _ pos -> pos
       PosR  _ pos -> pos
       PosN  _ pos -> pos
+      _ -> undefined
 
     getBool x = case x of
       PosL  b _ -> b
       PosR  b _ -> b
       PosN  b _ -> b
+      _ -> undefined
 
 synopsisSection :: EvalInfo -> [ManBlock]
 synopsisSection ei = [ S "SYNOPSIS", P (synopsis ei) ]
@@ -190,21 +194,21 @@
 makeCmdItems ei = case evalKind ei of
   Simple -> []
   Choice -> []
-  Main   -> sortBy (descCompare `on` fst) . foldl addCmd [] $ choices ei
+  Main   -> sortBy (descCompare `on` fst) . foldl' addCmd [] $ choices ei
   where
   addCmd acc ( ti, _ ) = ( termSec ti, I (label ti) (termDoc ti) )
                        : acc
   label ti = "$(b," ++ termName ti ++ ")"
 
 mergeOrphans :: ( [( String, ManBlock )], [Maybe ManBlock] ) -> [ManBlock]
-mergeOrphans ( orphans, marked ) = fst $ foldl go ( [], orphans ) marked
+mergeOrphans ( orphans, marked ) = fst $ foldl' go ( [], orphans ) marked
   where
   go ( acc, orphans ) (Just block) = ( block : acc, orphans )
   go ( acc, orphans ) Nothing      = ( acc',        []      )    
     where
     acc' = case orphans of
       []           -> acc
-      ( s, _ ) : _ -> let ( result, s' ) = foldl merge ( acc, s ) orphans
+      ( s, _ ) : _ -> let ( result, s' ) = foldl' merge ( acc, s ) orphans
                       in  S s' : result
 
   merge ( acc, secName ) ( secName', item )
@@ -215,7 +219,7 @@
            -> ( [( String, ManBlock )], [Maybe ManBlock] )
 mergeItems items blocks = ( orphans, marked )
   where
-  ( marked, _, _, orphans ) = foldl go ( [Nothing], [], False, items ) blocks
+  ( marked, _, _, orphans ) = foldl' go ( [Nothing], [], False, items ) blocks
   
   -- 'toInsert' is a list of manblocks that belong in the current section.
   go ( acc, toInsert, mark, items ) block = case block of
@@ -227,6 +231,7 @@
       ( toInsert', is' ) = first (map snd) $ partition ((== str) . fst) items
       acc'               = Just sec : marked
       mark'              = str == "DESCRIPTION"
+    transition _ = undefined
 
     marked = if mark then Nothing : acc' else acc'
       where
@@ -240,6 +245,7 @@
   cmp   = descCompare `on` fst
   items = sortBy cmp $ cmds ++ args
 
+eiSubst :: EvalInfo -> [( String, String )]
 eiSubst ei =
   [ ( "tname", termName . fst $ term ei )
   , ( "mname", termName . fst $ main ei )
diff --git a/src/System/Console/CmdTheLine/Manpage.hs b/src/System/Console/CmdTheLine/Manpage.hs
--- a/src/System/Console/CmdTheLine/Manpage.hs
+++ b/src/System/Console/CmdTheLine/Manpage.hs
@@ -19,7 +19,6 @@
 
 import Data.Maybe ( catMaybes )
 import Data.Char  ( isSpace )
-import Data.List  ( subsequences, words )
 
 import Text.Parsec
 import Text.PrettyPrint hiding ( char )
@@ -27,6 +26,7 @@
 type Subst = [( String, String )] -- An association list of
                                   -- ( replacing, replacement ) pairs.
 
+paragraphIndent, labelIndent :: Int
 paragraphIndent = 7
 labelIndent     = 4
 
@@ -52,17 +52,11 @@
 
   scan = many $ try (string "\\$") <|> try replace <|> pure <$> anyChar
 
-  replace = do
-    string "$("
-    replacement <- try escape <|> choice replacers <|> safeChars
-    char ')'
-    return replacement
+  replace = string "$(" >> content <* char ')'
+    where
+    content = try escape <|> choice replacers <|> safeChars
 
-  escape = do
-    c <- anyChar
-    char ','
-    str <- try replace <|> safeChars
-    return $ esc c str
+  escape = esc <$> (anyChar <* char ',') <*> try replace <|> safeChars
 
   safeChars = many1 $ satisfy (/= ')')
 
diff --git a/src/System/Console/CmdTheLine/Term.hs b/src/System/Console/CmdTheLine/Term.hs
--- a/src/System/Console/CmdTheLine/Term.hs
+++ b/src/System/Console/CmdTheLine/Term.hs
@@ -19,12 +19,10 @@
 import System.Console.CmdTheLine.Common
 import System.Console.CmdTheLine.CmdLine ( create )
 import System.Console.CmdTheLine.Arg
-import System.Console.CmdTheLine.ArgVal
 import qualified System.Console.CmdTheLine.Err     as E
 import qualified System.Console.CmdTheLine.Help    as H
 import qualified System.Console.CmdTheLine.Trie    as T
 
-import Control.Applicative hiding ( (<|>), empty )
 import Control.Arrow       ( second )
 import Control.Monad       ( join, (<=<) )
 
@@ -38,7 +36,6 @@
 import System.IO
 
 import Text.PrettyPrint
-import Text.Parsec
 
 
 --
@@ -90,36 +87,9 @@
 
 
 --
--- Terms as Applicative Functors
---
-
-instance Functor Term where
-  fmap = yield . result . result . fmap
-    where
-    yield f (Term ais y) = Term ais (f y)
-    result = (.)
-
-instance Applicative Term where
-  pure v = Term [] (\ _ _ -> return v)
-
-  (Term args f) <*> (Term args' v) = Term (args ++ args') wrapped
-    where
-    wrapped ei cl = f ei cl <*> v ei cl
-
-
---
 -- Standard Options
 --
 
-instance ArgVal HelpFormat where
-  converter = enum [ ( "pager", Pager )
-                   , ( "plain", Plain )
-                   , ( "groff", Groff )
-                   ]
-
-instance ArgVal (Maybe HelpFormat) where
-  converter = just
-
 addStdOpts :: EvalInfo -> ( Yield (Maybe HelpFormat)
                           , Maybe (Yield Bool)
                           , EvalInfo
@@ -208,7 +178,7 @@
     Left  T.Ambiguous -> throwError . UsageFail $ E.ambiguous com arg ambs
     where
     index = foldl add T.empty choices
-    add acc ( choice, _ ) = T.add acc (termName choice) choice
+    add acc ( choice, _ ) = T.add (termName choice) choice acc
 
     com  = "command"
     ambs = sort $ T.ambiguities index arg
@@ -268,7 +238,7 @@
 -- Share code between 'evalChoice' and 'unwrapChoice' with this HOF.
 evalChoiceBy :: ProcessTo a b
              -> [String] -> ( Term a, TermInfo ) -> [( Term a, TermInfo )] -> IO b
-evalChoiceBy method args mainTerm@( term, termInfo ) choices = do
+evalChoiceBy method args mainTerm@( _, termInfo ) choices = do
   ( chosen, args' ) <- either handleErr return =<<
     (runErrorT . fromErr $ chooseTerm termInfo eiChoices args)
 
diff --git a/src/System/Console/CmdTheLine/Trie.hs b/src/System/Console/CmdTheLine/Trie.hs
--- a/src/System/Console/CmdTheLine/Trie.hs
+++ b/src/System/Console/CmdTheLine/Trie.hs
@@ -2,9 +2,14 @@
  - This is open source software distributed under a MIT license.
  - See the file 'LICENSE' for further information.
  -}
-module System.Console.CmdTheLine.Trie where
+module System.Console.CmdTheLine.Trie
+  ( add, lookup, empty, isEmpty, fromList, ambiguities
+  , Trie, LookupFail(..)
+  ) where
 
+import Prelude hiding ( lookup )
 import qualified Data.Map as M
+import Data.List (foldl')
 
 {-
  - This implementation maps any non-ambiguous prefix of a key to its value.
@@ -16,12 +21,12 @@
              | Key a -- Value bound by an entire key.
              | Amb   -- No Value bound due to ambiguity in the key.
              | Nil   -- Attempt to retrieve a Value from an empty Trie.
-               deriving (Eq)
+               deriving ( Eq )
 
 data Trie a = Trie
   { val   :: Value a
-  , succs :: CMap (Trie a)
-  } deriving (Eq)
+  , nexts :: CMap (Trie a)
+  } deriving ( Eq )
 
 data LookupFail = Ambiguous | NotFound deriving (Show)
 
@@ -31,37 +36,31 @@
 isEmpty :: Eq a => Trie a -> Bool
 isEmpty = (== empty)
 
-add :: Trie a -> String -> a -> Trie a
-add t k v = go t k (length k) 0 v (Pre v {- Allocate less. -})
+add :: String -> a -> Trie a -> Trie a
+add k v t = go t k
   where
-  go t k len i v preV =
-    if i == len
-       then Trie (Key v) (succs t)
-       else Trie newVal  newSuccs
+  go t s = case s of
+    []     -> Trie (Key v) next
+    c:rest ->
+      let t'       = maybe empty id $ M.lookup c next
+          newNexts = M.insert c (go t' rest) next 
+      in Trie newVal newNexts
     where
-    newVal = case val t of
-      Amb       -> Amb
-      Pre _     -> Amb
-      v@(Key _) -> v
-      Nil       -> preV
+    next = nexts t
 
-    newSuccs = M.insert (k !! i) (go t' k len (i + 1) v preV) (succs t)
-      where
-      t' = maybe empty id $ M.lookup (k !! i) (succs t)
+    newVal = case val t of
+      Amb        -> Amb
+      Pre _      -> Amb
+      v'@(Key _) -> v'
+      Nil        -> Pre v
 
-findNode :: String -> Trie a -> Maybe (Trie a)
-findNode k t = go t k (length k) 0
+findNode :: Trie a -> String -> Maybe (Trie a)
+findNode t = foldl' go (Just t)
   where
-  go t k len i =
-    if i == len
-       then Just t
-       else goNext =<< M.lookup (k !! i) (succs t)
-    where
-    goNext t' = go t' k len (i + 1)
-
+  go acc c = M.lookup c . nexts =<< acc
 
 lookup :: String -> Trie a -> Either LookupFail a
-lookup k t = case findNode k t of
+lookup k t = case findNode t k of
   Nothing -> Left NotFound
   Just t' -> case val t' of
     Key v -> Right v
@@ -70,10 +69,10 @@
     Nil   -> Left  NotFound
 
 ambiguities :: Trie a -> String -> [String]
-ambiguities t pre = case findNode pre t of
+ambiguities t pre = case findNode t pre of
   Nothing -> []
   Just t' -> case val t' of
-    Amb -> go [] pre $ M.toList (succs t') : []
+    Amb -> go [] pre $ M.toList (nexts t') : []
     _   -> []
 
   where
@@ -87,7 +86,7 @@
       where
       ( c, t'' ) = top
 
-      assocs'    = M.toList (succs t'') : bottom : rest
+      assocs'    = M.toList (nexts t'') : bottom : rest
 
       pre'       = pre ++ return c
       acc'       = case val t'' of
@@ -95,7 +94,10 @@
         Nil   -> error "saw Nil on descent"
         _     -> acc
 
+    -- FIXME: Handle this better.  At least produce a meaningful error message.
+    descend _ = undefined
+
 fromList :: [( String, a )] -> Trie a
-fromList assoc = foldl consume empty assoc
+fromList assoc = foldl' consume empty assoc
   where
-  consume t ( k, v ) = add t k v
+  consume t ( k, v ) = add k v t
diff --git a/src/System/Console/CmdTheLine/Util.hs b/src/System/Console/CmdTheLine/Util.hs
--- a/src/System/Console/CmdTheLine/Util.hs
+++ b/src/System/Console/CmdTheLine/Util.hs
@@ -18,7 +18,6 @@
 
 import System.Console.CmdTheLine.Common
 import System.Console.CmdTheLine.Err
-import System.Console.CmdTheLine.Term
 
 import Control.Monad.IO.Class ( liftIO )
 
diff --git a/test/Main.hs b/test/Main.hs
--- a/test/Main.hs
+++ b/test/Main.hs
@@ -59,52 +59,50 @@
     return v)
 
 unwrapFB, unwrapAr, unwrapCP, unwrapCi :: [String] -> IO (Either EvalExit (IO ()))
-
-unwrapFB args = mute $ unwrap args ( FB.term, FB.termInfo )
-unwrapAr args = mute $ unwrap args ( Ar.arithTerm, Ar.termInfo )
-unwrapCP args = mute $ unwrap args ( CP.term, CP.termInfo )
-unwrapCi args = mute $
-  unwrapChoice args Ci.defaultTerm [ Ci.rotTerm, Ci.morseTerm ]
+unwrapFB args = unwrap args ( FB.term, FB.termInfo )
+unwrapAr args = unwrap args ( Ar.arithTerm, Ar.termInfo )
+unwrapCP args = unwrap args ( CP.term, CP.termInfo )
+unwrapCi args = unwrapChoice args Ci.defaultTerm [ Ci.rotTerm, Ci.morseTerm ]
 
 tests :: [Test]
 tests =
   -- With FizzBuzz we'll test the different forms of option assignment and
   -- flags.
   [ testGroup "FizzBuzz"
-    [ testCase "w/o args" . assert $ isRight <$> unwrapFB []
-    , testCase "w/ good args" . assert $
+    [ testCase " w/o args" . assert $ isRight <$> unwrapFB []
+    , testCase " w/ good args" . assert $
       isRight <$> unwrapFB [ "-q", "-s", "-v"
                            , "-f", "bob", "--buzz", "ann", "-t20"
                            ]
-    , testCase "w/ bad args" . assert $ isLeft <$> unwrapFB [ "-zork" ]
+    , testCase " w/ bad args" . assert $ isLeft <$> unwrapFB [ "-zork" ]
     ]
 
   -- With arith we'll test 'posRight' 'pos' positional argument partitioning.
   , testGroup "arith"
-    [ testCase "w/o args" . assert $ isLeft <$> unwrapAr []
-    , testCase "w/ good args many" . assert $
+    [ testCase " w/o args" . assert $ isLeft <$> unwrapAr []
+    , testCase " w/ good args many" . assert $
       isRight <$> unwrapAr [ "x^2+y*1", "x=2", "y=(11-1)/5" ]
-    , testCase "w/ good args one" . assert $
+    , testCase " w/ good args one" . assert $
       isRight <$> unwrapAr [ "x^2", "x=2" ]
-    , testCase "w/ bad args" . assert $
+    , testCase " w/ bad args" . assert $
       isLeft <$> unwrapAr [ "-pretty", "x^2", "x=2" ]
     ]
 
   -- With cipher we'll test subcommands.
   , testGroup "cipher"
-    [ testCase "w/o args" . assert $ isLeft <$> unwrapCi []
-    , testCase "morse" . assert $
+    [ testCase " w/o args" . assert $ isLeft <$> unwrapCi []
+    , testCase " morse" . assert $
       isRight <$> withInput ["bob"] (unwrapCi [ "morse" ])
-    , testCase "rot" . assert $
+    , testCase " rot" . assert $
       isRight <$> withInput ["bob"] (unwrapCi [ "rot" ])
     ]
 
   -- With cp we'll test 'revPosLeft' 'revPos' positional argument partitioning.
   , testGroup "cp"
-    [ testCase "w/o args" . assert $ isLeft <$> unwrapCP []
-    , testCase "w/ good args many" . assert $
+    [ testCase " w/o args" . assert $ isLeft <$> unwrapCP []
+    , testCase " w/ good args many" . assert $
       isRight <$> unwrapCP [ "-d", "cmdtheline.cabal", "LICENSE", "test" ]
-    , testCase "w/ good args one" . assert $
+    , testCase " w/ good args one" . assert $
       isRight <$> unwrapCP [ "-d", "cmdtheline.cabal", "foo" ]
     ]
   ]