main: Switch to sub-command style CLI

This introduces the new sub-command `refine` that does what running the
binary without sub-command previously did.

This opens up the possibility for further sub-commands and improves
discoverability.

README.md

@@ -11,11 +11,13 @@ In the absence of a project name: This is my master's thesis
 There isn't much to see, yet. To see pretty printed parse results,
 use:
 
-    stack exec ma < FILENAME
+    stack exec ma refine < FILENAME
 
 Where `FILENAME` is a file describing the input. Examples are in
 `examples/`.
 
+Command line syntax is described in `stack exec -- ma --help`.
+
 ## API documentation
 
 The documentation for the internal API can be built and opened in the

src/main/Main.hs

@@ -28,15 +28,31 @@ import           MA.FunctorDescription
 
 
 data Options = Options
-  { optVerbose :: Bool
-  , optCommand :: Maybe SubCommand
-  }
+  { optCommand :: SubCommand }
 
-data SubCommand = HelpCommand (HelpCommand)
+data SubCommand
+  = HelpCommand HelpCommand
+  | RefineCommand RefineOptions
 
 subcommand :: Parser SubCommand
-subcommand = hsubparser $
-  command "help" (info (HelpCommand <$> helpCommand) (progDesc "get help"))
+subcommand =
+  hsubparser
+    (command "help" (info (HelpCommand <$> helpCommand) (progDesc "get help"))) <|>
+  hsubparser
+    (command
+       "refine"
+       (info
+          (RefineCommand <$> refineOptions)
+          (progDesc
+             "Refine the initial partition of a given coalgebra and output the result as a list of blocks of states.")))
+
+data RefineOptions = RefineOptions
+  { refineStats :: Bool
+  }
+
+refineOptions :: Parser RefineOptions
+refineOptions = RefineOptions
+  <$> switch ( long "stats" <> help "Print runtime statistics (such as timing information) to stderr")
 
 data HelpCommand = HelpListFunctors
 
@@ -44,12 +60,7 @@ helpCommand :: Parser HelpCommand
 helpCommand = subparser $ command "list_functors" (info (pure HelpListFunctors) (progDesc "list available functors"))
 
 options :: Parser Options
-options = Options
-  <$> switch (  long "verbose"
-             <> short 'v'
-             <> help "Print runtime stats"
-             )
-  <*> optional subcommand
+options = Options <$> subcommand
 
 main :: IO ()
 main = do
@@ -58,16 +69,16 @@ main = do
     info (options <**> helper) fullDesc
 
   case optCommand params of
-    Just (HelpCommand h) -> printHelp h
-    Nothing -> do
-      (f, (symbolTable, encoding)) <- withTime (optVerbose params) "parse" $ do
+    (HelpCommand h) -> printHelp h
+    (RefineCommand r) -> do
+      (f, (symbolTable, encoding)) <- withTime (refineStats r) "parse" $ do
         readCoalgebraFromStdin >>= \case
           Left err -> hPutStrLn stderr err >> exitFailure
           Right res -> evaluate $ res
 
-      partition <- withTime (optVerbose params) "refine"
+      partition <- withTime (refineStats r) "refine"
         (stToIO (refine f encoding))
-      withTime (optVerbose params) "print"
+      withTime (refineStats r) "print"
         (printPartition encoding symbolTable partition)
 
 printHelp :: HelpCommand -> IO ()