X-Git-Url: http://git.megacz.com/?a=blobdiff_plain;f=compiler%2Fghci%2FInteractiveUI.hs;h=74133dd2ad091397b2490e8e44e7823bcacf9028;hb=27e9c93a8445fbabb4c1cb6f77e3a4e7d9a4ffd0;hp=ad708f511f6f3c2dcf42033abde655dfb35fcd92;hpb=e1b8996040150d5b4027ebd50c2df1f24d79a531;p=ghc-hetmet.git

diff --git a/compiler/ghci/InteractiveUI.hs b/compiler/ghci/InteractiveUI.hs
index ad708f5..74133dd 100644
--- a/compiler/ghci/InteractiveUI.hs
+++ b/compiler/ghci/InteractiveUI.hs
@@ -70,10 +70,12 @@ import System.Exit	( exitWith, ExitCode(..) )
 import System.Directory
 import System.IO
 import System.IO.Error as IO
+import System.FilePath
 import Data.Char
 import Data.Dynamic
 import Data.Array
 import Control.Monad as Monad
+import Text.Printf
 
 import Foreign.StablePtr	( newStablePtr )
 import GHC.Exts		( unsafeCoerce# )
@@ -108,7 +110,8 @@ builtin_commands = [
   ("browse",    keepGoing browseCmd,		False, completeModule),
   ("cd",    	keepGoing changeDirectory,	False, completeFilename),
   ("check",	keepGoing checkModule,		False, completeHomeModule),
-  ("continue",  continueCmd,                    False, completeNone),
+  ("continue",  keepGoing continueCmd,          False, completeNone),
+  ("cmd",       keepGoing cmdCmd,               False, completeIdentifier),
   ("ctags",	keepGoing createCTagsFileCmd, 	False, completeFilename),
   ("def",	keepGoing defineMacro,		False, completeIdentifier),
   ("delete",    keepGoing deleteCmd,            False, completeNone),
@@ -131,9 +134,9 @@ builtin_commands = [
   ("set",	keepGoing setCmd,		True,  completeSetOptions),
   ("show",	keepGoing showCmd,		False, completeNone),
   ("sprint",    keepGoing sprintCmd,            False, completeIdentifier),
-  ("step",      stepCmd,                        False, completeIdentifier), 
+  ("step",      keepGoing stepCmd,              False, completeIdentifier), 
   ("type",	keepGoing typeOfExpr,		False, completeIdentifier),
-  ("trace",     traceCmd,                       False, completeIdentifier), 
+  ("trace",     keepGoing traceCmd,             False, completeIdentifier), 
   ("undef",     keepGoing undefineMacro,	False, completeMacro),
   ("unset",	keepGoing unsetOptions,		True,  completeSetOptions)
   ]
@@ -149,31 +152,49 @@ shortHelpText = "use :? for help.\n"
 helpText =
  " Commands available from the prompt:\n" ++
  "\n" ++
- "   <stmt>                      evaluate/run <stmt>\n" ++
+ "   <statement>                 evaluate/run <statement>\n" ++
  "   :add <filename> ...         add module(s) to the current target set\n" ++
- "   :abandon                    at a breakpoint, abandon current computation\n" ++
- "   :break [<mod>] <l> [<col>]  set a breakpoint at the specified location\n" ++
- "   :break <name>               set a breakpoint on the specified function\n" ++
  "   :browse [*]<module>         display the names defined by <module>\n" ++
  "   :cd <dir>                   change directory to <dir>\n" ++
- "   :continue                   resume after a breakpoint\n" ++
+ "   :cmd <expr>                 run the commands returned by <expr>::IO String"++
  "   :ctags [<file>]             create tags file for Vi (default: \"tags\")\n" ++
  "   :def <cmd> <expr>           define a command :<cmd>\n" ++
- "   :delete <number>            delete the specified breakpoint\n" ++
- "   :delete *                   delete all breakpoints\n" ++
  "   :edit <file>                edit file\n" ++
  "   :edit                       edit last module\n" ++
  "   :etags [<file>]             create tags file for Emacs (default: \"TAGS\")\n" ++
--- "   :force <expr>               print <expr>, forcing unevaluated parts\n" ++
  "   :help, :?                   display this list of commands\n" ++
  "   :info [<name> ...]          display information about the given names\n" ++
  "   :kind <type>                show the kind of <type>\n" ++
  "   :load <filename> ...        load module(s) and their dependents\n" ++
  "   :module [+/-] [*]<mod> ...  set the context for expression evaluation\n" ++
  "   :main [<arguments> ...]     run the main function with the given arguments\n" ++
- "   :print [<name> ...]         prints a value without forcing its computation\n" ++
  "   :quit                       exit GHCi\n" ++
  "   :reload                     reload the current module set\n" ++
+ "   :type <expr>                show the type of <expr>\n" ++
+ "   :undef <cmd>                undefine user-defined command :<cmd>\n" ++
+ "   :!<command>                 run the shell command <command>\n" ++
+ "\n" ++
+ " -- Commands for debugging:\n" ++
+ "\n" ++
+ "   :abandon                    at a breakpoint, abandon current computation\n" ++
+ "   :back                       go back in the history (after :trace)\n" ++
+ "   :break [<mod>] <l> [<col>]  set a breakpoint at the specified location\n" ++
+ "   :break <name>               set a breakpoint on the specified function\n" ++
+ "   :continue                   resume after a breakpoint\n" ++
+ "   :delete <number>            delete the specified breakpoint\n" ++
+ "   :delete *                   delete all breakpoints\n" ++
+ "   :force <expr>               print <expr>, forcing unevaluated parts\n" ++
+ "   :forward                    go forward in the history (after :back)\n" ++
+ "   :history [<n>]              show the last <n> items in the history (after :trace)\n" ++
+ "   :print [<name> ...]         prints a value without forcing its computation\n" ++
+ "   :sprint [<name> ...]        simplifed version of :print\n" ++
+ "   :step                       single-step after stopping at a breakpoint\n"++
+ "   :step <expr>                single-step into <expr>\n"++
+ "   :trace                      trace after stopping at a breakpoint\n"++
+ "   :trace <expr>               trace into <expr> (remembers breakpoints for :history)\n"++
+
+ "\n" ++
+ " -- Commands for changing settings:\n" ++
  "\n" ++
  "   :set <option> ...           set options\n" ++
  "   :set args <arg> ...         set the arguments returned by System.getArgs\n" ++
@@ -181,29 +202,24 @@ helpText =
  "   :set prompt <prompt>        set the prompt used in GHCi\n" ++
  "   :set editor <cmd>           set the command used for :edit\n" ++
  "   :set stop <cmd>             set the command to run when a breakpoint is hit\n" ++
- "\n" ++
- "   :show breaks                show active breakpoints\n" ++
- "   :show context               show the breakpoint context\n" ++
- "   :show modules               show the currently loaded modules\n" ++
- "   :show bindings              show the current bindings made at the prompt\n" ++
- "\n" ++
- "   :sprint [<name> ...]        simplifed version of :print\n" ++
- "   :step                       single-step after stopping at a breakpoint\n"++
- "   :step <expr>                single-step into <expr>\n"++
- "   :type <expr>                show the type of <expr>\n" ++
- "   :undef <cmd>                undefine user-defined command :<cmd>\n" ++
  "   :unset <option> ...         unset options\n" ++
- "   :!<command>                 run the shell command <command>\n" ++
  "\n" ++
- " Options for ':set' and ':unset':\n" ++
+ "  Options for ':set' and ':unset':\n" ++
  "\n" ++
  "    +r            revert top-level expressions after each evaluation\n" ++
  "    +s            print timing/memory stats after each evaluation\n" ++
  "    +t            print type after evaluation\n" ++
  "    -<flags>      most GHC command line flags can also be set here\n" ++
  "                         (eg. -v2, -fglasgow-exts, etc.)\n" ++
+ "\n" ++
+ " -- Commands for displaying information:\n" ++
+ "\n" ++
+ "   :show bindings              show the current bindings made at the prompt\n" ++
+ "   :show breaks                show the active breakpoints\n" ++
+ "   :show context               show the breakpoint context\n" ++
+ "   :show modules               show the currently loaded modules\n" ++
+ "   :show <setting>             show anything that can be set with :set (e.g. args)\n" ++
  "\n" 
--- Todo: add help for breakpoint commands here
 
 findEditor = do
   getEnv "EDITOR" 
@@ -274,7 +290,8 @@ interactiveUI session srcs maybe_expr = do
                    prelude = prel_mod,
                    break_ctr = 0,
                    breaks = [],
-                   tickarrays = emptyModuleEnv
+                   tickarrays = emptyModuleEnv,
+                   cmdqueue = []
                  }
 
 #ifdef USE_READLINE
@@ -433,17 +450,9 @@ fileLoop hdl show_prompt = do
 	Right l -> 
 	  case removeSpaces l of
             "" -> fileLoop hdl show_prompt
-	    l  -> do quit <- runCommand l
+	    l  -> do quit <- runCommands l
                      if quit then return () else fileLoop hdl show_prompt
 
-stringLoop :: [String] -> GHCi Bool{-True: we quit-}
-stringLoop [] = return False
-stringLoop (s:ss) = do
-   case removeSpaces s of
-	"" -> stringLoop ss
-	l  -> do quit <- runCommand l
-                 if quit then return True else stringLoop ss
-
 mkPrompt = do
   session <- getSession
   (toplevs,exports) <- io (GHC.getContext session)
@@ -501,17 +510,31 @@ readlineLoop = do
 	    "" -> readlineLoop
 	    l  -> do
         	  io (addHistory l)
-  	  	  quit <- runCommand l
+  	  	  quit <- runCommands l
           	  if quit then return () else readlineLoop
 #endif
 
-runCommand :: String -> GHCi Bool
-runCommand c = ghciHandle handler (doCommand c)
-  where 
-    doCommand (':' : command) = specialCommand command
-    doCommand stmt
-       = do timeIt $ runStmt stmt GHC.RunToCompletion
-            return False
+runCommands :: String -> GHCi Bool
+runCommands cmd = do
+        q <- ghciHandle handler (doCommand cmd)
+        if q then return True else runNext
+  where
+       runNext = do
+          st <- getGHCiState
+          case cmdqueue st of
+            []   -> return False
+            c:cs -> do setGHCiState st{ cmdqueue = cs }
+                       runCommands c
+
+       doCommand (':' : cmd) = specialCommand cmd
+       doCommand stmt        = do timeIt $ runStmt stmt GHC.RunToCompletion
+                                  return False
+
+enqueueCommands :: [String] -> GHCi ()
+enqueueCommands cmds = do
+  st <- getGHCiState
+  setGHCiState st{ cmdqueue = cmds ++ cmdqueue st }
+
 
 -- This version is for the GHC command-line option -e.  The only difference
 -- from runCommand is that it catches the ExitException exception and
@@ -533,55 +556,54 @@ runCommandEval c = ghciHandle handleEval (doCommand c)
 runStmt :: String -> SingleStep -> GHCi Bool
 runStmt stmt step
  | null (filter (not.isSpace) stmt) = return False
+ | ["import", mod] <- words stmt    = keepGoing setContext ('+':mod)
  | otherwise
  = do st <- getGHCiState
       session <- getSession
       result <- io $ withProgName (progname st) $ withArgs (args st) $
 	     	     GHC.runStmt session stmt step
       afterRunStmt result
-      return False
 
 
-afterRunStmt :: GHC.RunResult -> GHCi (Maybe (Bool,[Name]))
+afterRunStmt :: GHC.RunResult -> GHCi Bool
+                                 -- False <=> the statement failed to compile
+afterRunStmt (GHC.RunException e) = throw e
 afterRunStmt run_result = do
-  mb_result <- switchOnRunResult run_result
-  -- possibly print the type and revert CAFs after evaluating an expression
-  show_types <- isOptionSet ShowType
   session <- getSession
-  case mb_result of
-    Nothing    -> return ()      
-    Just (is_break,names) -> 
-            when (is_break || show_types) $
-                  mapM_ (showTypeOfName session) names
-  
+  case run_result of
+     GHC.RunOk names -> do
+        show_types <- isOptionSet ShowType
+        when show_types $ mapM_ (showTypeOfName session) names
+     GHC.RunBreak _ names mb_info -> do
+        resumes <- io $ GHC.getResumeContext session
+        printForUser $ ptext SLIT("Stopped at") <+> 
+                       ppr (GHC.resumeSpan (head resumes))
+        mapM_ (showTypeOfName session) names
+        maybe (return ()) runBreakCmd mb_info
+        -- run the command set with ":set stop <cmd>"
+        st <- getGHCiState
+        enqueueCommands [stop st]
+        return ()
+     _ -> return ()
+
   flushInterpBuffers
   io installSignalHandlers
   b <- isOptionSet RevertCAFs
   io (when b revertCAFs)
 
-  return mb_result
-
-
-switchOnRunResult :: GHC.RunResult -> GHCi (Maybe (Bool,[Name]))
-switchOnRunResult GHC.RunFailed = return Nothing
-switchOnRunResult (GHC.RunException e) = throw e
-switchOnRunResult (GHC.RunOk names) = return $ Just (False,names)
-switchOnRunResult (GHC.RunBreak threadId names info) = do
-   session <- getSession
-   Just mod_info <- io $ GHC.getModuleInfo session (GHC.breakInfo_module info) 
-   let modBreaks  = GHC.modInfoModBreaks mod_info
-   let ticks      = GHC.modBreaks_locs modBreaks
-
-   -- display information about the breakpoint
-   let location = ticks ! GHC.breakInfo_number info
-   printForUser $ ptext SLIT("Stopped at") <+> ppr location
-
-   -- run the command set with ":set stop <cmd>"
-   st <- getGHCiState
-   runCommand (stop st)
-
-   return (Just (True,names))
+  return (case run_result of GHC.RunOk _ -> True; _ -> False)
 
+runBreakCmd :: GHC.BreakInfo -> GHCi ()
+runBreakCmd info = do
+  let mod = GHC.breakInfo_module info
+      nm  = GHC.breakInfo_number info
+  st <- getGHCiState
+  case  [ loc | (i,loc) <- breaks st,
+                breakModule loc == mod, breakTick loc == nm ] of
+        []  -> return ()
+        loc:_ | null cmd  -> return ()
+              | otherwise -> do enqueueCommands [cmd]; return ()
+              where cmd = onBreakCmd loc
 
 showTypeOfName :: Session -> Name -> GHCi ()
 showTypeOfName session n
@@ -675,8 +697,7 @@ pprInfo exts (thing, fixity, insts)
 runMain :: String -> GHCi ()
 runMain args = do
   let ss = concat $ intersperse "," (map (\ s -> ('"':s)++"\"") (toArgs args))
-  runCommand $ '[': ss ++ "] `System.Environment.withArgs` main"
-  return ()
+  enqueueCommands  ['[': ss ++ "] `System.Environment.withArgs` main"]
 
 addModule :: [FilePath] -> GHCi ()
 addModule files = do
@@ -702,25 +723,47 @@ changeDirectory dir = do
   io (setCurrentDirectory dir)
 
 editFile :: String -> GHCi ()
-editFile str
-  | null str  = do
-	-- find the name of the "topmost" file loaded
-     session <- getSession
-     graph0 <- io (GHC.getModuleGraph session)
-     graph1 <- filterM (io . GHC.isLoaded session . GHC.ms_mod_name) graph0
-     let graph2 = flattenSCCs (GHC.topSortModuleGraph True graph1 Nothing)
-     case GHC.ml_hs_file (GHC.ms_location (last graph2)) of
-	Just file -> do_edit file
-	Nothing   -> throwDyn (CmdLineError "unknown file name")
-  | otherwise = do_edit str
-  where
-	do_edit file = do
-	   st <- getGHCiState
-	   let cmd = editor st
-	   when (null cmd) $ 
-		throwDyn (CmdLineError "editor not set, use :set editor")
-	   io $ system (cmd ++ ' ':file)
-           return ()
+editFile str =
+  do file <- if null str then chooseEditFile else return str
+     st <- getGHCiState
+     let cmd = editor st
+     when (null cmd) 
+       $ throwDyn (CmdLineError "editor not set, use :set editor")
+     io $ system (cmd ++ ' ':file)
+     return ()
+
+-- The user didn't specify a file so we pick one for them.
+-- Our strategy is to pick the first module that failed to load,
+-- or otherwise the first target.
+--
+-- XXX: Can we figure out what happened if the depndecy analysis fails
+--      (e.g., because the porgrammeer mistyped the name of a module)?
+-- XXX: Can we figure out the location of an error to pass to the editor?
+-- XXX: if we could figure out the list of errors that occured during the
+-- last load/reaload, then we could start the editor focused on the first
+-- of those.
+chooseEditFile :: GHCi String
+chooseEditFile =
+  do session <- getSession
+     let hasFailed x = io $ fmap not $ GHC.isLoaded session $ GHC.ms_mod_name x
+
+     graph <- io (GHC.getModuleGraph session)
+     failed_graph <- filterM hasFailed graph
+     let order g  = flattenSCCs $ GHC.topSortModuleGraph True g Nothing
+         pick xs  = case xs of
+                      x : _ -> GHC.ml_hs_file (GHC.ms_location x)
+                      _     -> Nothing
+
+     case pick (order failed_graph) of
+       Just file -> return file
+       Nothing   -> 
+         do targets <- io (GHC.getTargets session)
+            case msum (map fromTarget targets) of
+              Just file -> return file
+              Nothing   -> throwDyn (CmdLineError "No files to edit.")
+          
+  where fromTarget (GHC.Target (GHC.TargetFile f _) _) = Just f
+        fromTarget _ = Nothing -- when would we get a module target?
 
 defineMacro :: String -> GHCi ()
 defineMacro s = do
@@ -749,7 +792,8 @@ defineMacro s = do
 runMacro :: GHC.HValue{-String -> IO String-} -> String -> GHCi Bool
 runMacro fun s = do
   str <- io ((unsafeCoerce# fun :: String -> IO String) s)
-  stringLoop (lines str)
+  enqueueCommands (lines str)
+  return False
 
 undefineMacro :: String -> GHCi ()
 undefineMacro macro_name = do
@@ -764,6 +808,17 @@ undefineMacro macro_name = do
 	else do
   io (writeIORef commands (filter ((/= macro_name) . cmdName) cmds))
 
+cmdCmd :: String -> GHCi ()
+cmdCmd str = do
+  let expr = '(' : str ++ ") :: IO String"
+  session <- getSession
+  maybe_hv <- io (GHC.compileExpr session expr)
+  case maybe_hv of
+    Nothing -> return ()
+    Just hv -> do 
+        cmds <- io $ (unsafeCoerce# hv :: IO String)
+        enqueueCommands (lines cmds)
+        return ()
 
 loadModule :: [(FilePath, Maybe Phase)] -> GHCi SuccessFlag
 loadModule fs = timeIt (loadModule' fs)
@@ -776,6 +831,7 @@ loadModule' files = do
   session <- getSession
 
   -- unload first
+  discardActiveBreakPoints
   io (GHC.setTargets session [])
   io (GHC.load session LoadAllTargets)
 
@@ -791,9 +847,7 @@ loadModule' files = do
   -- as a ToDo for now.
 
   io (GHC.setTargets session targets)
-  ok <- io (GHC.load session LoadAllTargets)
-  afterLoad ok session
-  return ok
+  doLoad session LoadAllTargets
 
 checkModule :: String -> GHCi ()
 checkModule m = do
@@ -816,19 +870,28 @@ checkModule m = do
 reloadModule :: String -> GHCi ()
 reloadModule "" = do
   io (revertCAFs)		-- always revert CAFs on reload.
+  discardActiveBreakPoints
   session <- getSession
-  ok <- io (GHC.load session LoadAllTargets)
-  afterLoad ok session
+  doLoad session LoadAllTargets
+  return ()
 reloadModule m = do
   io (revertCAFs)		-- always revert CAFs on reload.
+  discardActiveBreakPoints
   session <- getSession
-  ok <- io (GHC.load session (LoadUpTo (GHC.mkModuleName m)))
+  doLoad session (LoadUpTo (GHC.mkModuleName m))
+  return ()
+
+doLoad session howmuch = do
+  -- turn off breakpoints before we load: we can't turn them off later, because
+  -- the ModBreaks will have gone away.
+  discardActiveBreakPoints
+  ok <- io (GHC.load session howmuch)
   afterLoad ok session
+  return ok
 
 afterLoad ok session = do
   io (revertCAFs)  -- always revert CAFs on load.
   discardTickArrays
-  discardActiveBreakPoints
   graph <- io (GHC.getModuleGraph session)
   graph' <- filterM (io . GHC.isLoaded session . GHC.ms_mod_name) graph
   setContextAfterLoad session graph'
@@ -917,8 +980,8 @@ browseCmd m =
 
 browseModule m exports_only = do
   s <- getSession
-  modl <- if exports_only then lookupModule s m
-                          else wantInterpretedModule s m
+  modl <- if exports_only then lookupModule m
+                          else wantInterpretedModule m
 
   -- Temporarily set the context to the module we're interested in,
   -- just so we can get an appropriate PrintUnqualified
@@ -1057,6 +1120,19 @@ setEditor cmd = do
   st <- getGHCiState
   setGHCiState st{ editor = cmd }
 
+setStop str@(c:_) | isDigit c
+  = do let (nm_str,rest) = break (not.isDigit) str
+           nm = read nm_str
+       st <- getGHCiState
+       let old_breaks = breaks st
+       if all ((/= nm) . fst) old_breaks
+              then printForUser (text "Breakpoint" <+> ppr nm <+>
+                                 text "does not exist")
+              else do
+       let new_breaks = map fn old_breaks
+           fn (i,loc) | i == nm   = (i,loc { onBreakCmd = dropWhile isSpace rest })
+                      | otherwise = (i,loc)
+       setGHCiState st{ breaks = new_breaks }
 setStop cmd = do
   st <- getGHCiState
   setGHCiState st{ stop = cmd }
@@ -1074,8 +1150,10 @@ setOptions wds =
    do -- first, deal with the GHCi opts (+s, +t, etc.)
       let (plus_opts, minus_opts)  = partition isPlus wds
       mapM_ setOpt plus_opts
-
       -- then, dynamic flags
+      newDynFlags minus_opts
+
+newDynFlags minus_opts = do
       dflags <- getDynFlags
       let pkg_flags = packageFlags dflags
       (dflags',leftovers) <- io $ GHC.parseDynamicFlags dflags minus_opts
@@ -1113,10 +1191,11 @@ unsetOptions str
 
        mapM_ unsetOpt plus_opts
  
-       -- can't do GHC flags for now
-       if (not (null minus_opts))
-	  then throwDyn (CmdLineError "can't unset GHC command-line flags")
-	  else return ()
+       let no_flag ('-':'f':rest) = return ("-fno-" ++ rest)
+           no_flag f = throwDyn (ProgramError ("don't know how to reverse " ++ f))
+
+       no_flags <- mapM no_flag minus_opts
+       newDynFlags no_flags
 
 isMinus ('-':s) = True
 isMinus _ = False
@@ -1148,14 +1227,20 @@ optToStr RevertCAFs = "r"
 -- ---------------------------------------------------------------------------
 -- code for `:show'
 
-showCmd str =
+showCmd str = do
+  st <- getGHCiState
   case words str of
+        ["args"]     -> io $ putStrLn (show (args st))
+        ["prog"]     -> io $ putStrLn (show (progname st))
+        ["prompt"]   -> io $ putStrLn (show (prompt st))
+        ["editor"]   -> io $ putStrLn (show (editor st))
+        ["stop"]     -> io $ putStrLn (show (stop st))
 	["modules" ] -> showModules
 	["bindings"] -> showBindings
 	["linker"]   -> io showLinkerState
-        ["breaks"] -> showBkptTable
-        ["context"] -> showContext
-	_ -> throwDyn (CmdLineError "syntax:  :show [modules|bindings|breaks]")
+        ["breaks"]   -> showBkptTable
+        ["context"]  -> showContext
+	_ -> throwDyn (CmdLineError "syntax:  :show [args|prog|prompt|editor|stop|modules|bindings|breaks|context]")
 
 showModules = do
   session <- getSession
@@ -1376,6 +1461,28 @@ expandPath path =
    other -> 
 	return other
 
+wantInterpretedModule :: String -> GHCi Module
+wantInterpretedModule str = do
+   session <- getSession
+   modl <- lookupModule str
+   is_interpreted <- io (GHC.moduleIsInterpreted session modl)
+   when (not is_interpreted) $
+       throwDyn (CmdLineError ("module '" ++ str ++ "' is not interpreted"))
+   return modl
+
+wantNameFromInterpretedModule noCanDo str and_then = do
+   session <- getSession
+   names <- io $ GHC.parseName session str
+   case names of
+      []    -> return ()
+      (n:_) -> do
+            let modl = GHC.nameModule n
+            is_interpreted <- io (GHC.moduleIsInterpreted session modl)
+            if not is_interpreted
+               then noCanDo n $ text "module " <> ppr modl <>
+                                text " is not interpreted"
+               else and_then n
+
 -- ----------------------------------------------------------------------------
 -- Windows console setup
 
@@ -1411,26 +1518,23 @@ pprintCommand bind force str = do
   session <- getSession
   io $ pprintClosureCommand session bind force str
 
-stepCmd :: String -> GHCi Bool
+stepCmd :: String -> GHCi ()
 stepCmd []         = doContinue GHC.SingleStep
-stepCmd expression = runStmt expression GHC.SingleStep
+stepCmd expression = do runStmt expression GHC.SingleStep; return ()
 
-traceCmd :: String -> GHCi Bool
+traceCmd :: String -> GHCi ()
 traceCmd []         = doContinue GHC.RunAndLogSteps
-traceCmd expression = runStmt expression GHC.RunAndLogSteps
+traceCmd expression = do runStmt expression GHC.RunAndLogSteps; return ()
 
-continueCmd :: String -> GHCi Bool
-continueCmd [] = doContinue GHC.RunToCompletion
-continueCmd other = do
-   io $ putStrLn "The continue command accepts no arguments."
-   return False
+continueCmd :: String -> GHCi ()
+continueCmd = noArgs $ doContinue GHC.RunToCompletion
 
-doContinue :: SingleStep -> GHCi Bool
+doContinue :: SingleStep -> GHCi ()
 doContinue step = do 
   session <- getSession
   runResult <- io $ GHC.resume session step
   afterRunStmt runResult
-  return False
+  return ()
 
 abandonCmd :: String -> GHCi ()
 abandonCmd = noArgs $ do
@@ -1457,15 +1561,23 @@ deleteCmd argLine = do
          | otherwise = return ()
 
 historyCmd :: String -> GHCi ()
-historyCmd = noArgs $ do
-  s <- getSession
-  resumes <- io $ GHC.getResumeContext s
-  case resumes of
-    [] -> io $ putStrLn "Not stopped at a breakpoint"
-    (r:rs) -> do
-      let hist = GHC.resumeHistory r
-      spans <- mapM (io . GHC.getHistorySpan s) hist
-      printForUser (vcat (map ppr spans))
+historyCmd arg
+  | null arg        = history 20
+  | all isDigit arg = history (read arg)
+  | otherwise       = io $ putStrLn "Syntax:  :history [num]"
+  where
+  history num = do
+    s <- getSession
+    resumes <- io $ GHC.getResumeContext s
+    case resumes of
+      [] -> io $ putStrLn "Not stopped at a breakpoint"
+      (r:rs) -> do
+        let hist = GHC.resumeHistory r
+            (took,rest) = splitAt num hist
+        spans <- mapM (io . GHC.getHistorySpan s) took
+        let nums = map (printf "-%-3d:") [(1::Int)..]
+        printForUser (vcat (zipWith (<+>) (map text nums) (map ppr spans)))
+        io $ putStrLn $ if null rest then "<end of history>" else "..."
 
 backCmd :: String -> GHCi ()
 backCmd = noArgs $ do
@@ -1475,8 +1587,7 @@ backCmd = noArgs $ do
   mapM_ (showTypeOfName s) names
    -- run the command set with ":set stop <cmd>"
   st <- getGHCiState
-  runCommand (stop st)
-  return ()
+  enqueueCommands [stop st]
 
 forwardCmd :: String -> GHCi ()
 forwardCmd = noArgs $ do
@@ -1488,8 +1599,7 @@ forwardCmd = noArgs $ do
   mapM_ (showTypeOfName s) names
    -- run the command set with ":set stop <cmd>"
   st <- getGHCiState
-  runCommand (stop st)
-  return ()
+  enqueueCommands [stop st]
 
 -- handle the "break" command
 breakCmd :: String -> GHCi ()
@@ -1502,7 +1612,7 @@ breakSwitch _session [] = do
    io $ putStrLn "The break command requires at least one argument."
 breakSwitch session args@(arg1:rest) 
    | looksLikeModuleName arg1 = do
-        mod <- wantInterpretedModule session arg1
+        mod <- wantInterpretedModule arg1
         breakByModule session mod rest
    | all isDigit arg1 = do
         (toplevel, _) <- io $ GHC.getContext session 
@@ -1511,38 +1621,19 @@ breakSwitch session args@(arg1:rest)
            [] -> do 
               io $ putStrLn "Cannot find default module for breakpoint." 
               io $ putStrLn "Perhaps no modules are loaded for debugging?"
-   | otherwise = do -- assume it's a name
-        names <- io $ GHC.parseName session arg1
-        case names of
-          []    -> return ()
-          (n:_) -> do
-            let loc  = GHC.nameSrcLoc n
-                modl = GHC.nameModule n
-            is_interpreted <- io (GHC.moduleIsInterpreted session modl)
-            if not is_interpreted
-               then noCanDo $ text "module " <> ppr modl <>
-                              text " is not interpreted"
-               else do
-            if GHC.isGoodSrcLoc loc
-               then findBreakAndSet (GHC.nameModule n) $ 
+   | otherwise = do -- try parsing it as an identifier
+        wantNameFromInterpretedModule noCanDo arg1 $ \name -> do
+        let loc = GHC.srcSpanStart (GHC.nameSrcSpan name)
+        if GHC.isGoodSrcLoc loc
+               then findBreakAndSet (GHC.nameModule name) $ 
                          findBreakByCoord (Just (GHC.srcLocFile loc))
                                           (GHC.srcLocLine loc, 
                                            GHC.srcLocCol loc)
-               else noCanDo $ text "can't find its location: " <>
-                              ppr loc
-           where
-             noCanDo why = printForUser $
+               else noCanDo name $ text "can't find its location: " <> ppr loc
+       where
+          noCanDo n why = printForUser $
                 text "cannot set breakpoint on " <> ppr n <> text ": " <> why
 
-
-wantInterpretedModule :: Session -> String -> GHCi Module
-wantInterpretedModule session str = do
-   modl <- io $ GHC.findModule session (GHC.mkModuleName str) Nothing
-   is_interpreted <- io (GHC.moduleIsInterpreted session modl)
-   when (not is_interpreted) $
-       throwDyn (CmdLineError ("module '" ++ str ++ "' is not interpreted"))
-   return modl
-
 breakByModule :: Session -> Module -> [String] -> GHCi () 
 breakByModule session mod args@(arg1:rest)
    | all isDigit arg1 = do  -- looks like a line number
@@ -1572,6 +1663,7 @@ findBreakAndSet mod lookupTickTree = do
                              { breakModule = mod
                              , breakLoc = span
                              , breakTick = tick
+                             , onBreakCmd = ""
                              }
                printForUser $
                   text "Breakpoint " <> ppr nm <>
@@ -1609,7 +1701,8 @@ findBreakByCoord :: Maybe FastString -> (Int,Int) -> TickArray
 findBreakByCoord mb_file (line, col) arr
   | not (inRange (bounds arr) line) = Nothing
   | otherwise =
-    listToMaybe (sortBy rightmost contains)
+    listToMaybe (sortBy rightmost contains) `mplus`
+    listToMaybe (sortBy leftmost_smallest after_here)
   where 
         ticks = arr ! line
 
@@ -1621,6 +1714,10 @@ findBreakByCoord mb_file (line, col) arr
                  | Just f <- mb_file = GHC.srcSpanFile span == f
                  | otherwise         = True
 
+        after_here = [ tick | tick@(nm,span) <- ticks,
+                              GHC.srcSpanStartLine span == line,
+                              GHC.srcSpanStartCol span >= col ]
+
 
 leftmost_smallest  (_,a) (_,b) = a `compare` b
 leftmost_largest   (_,a) (_,b) = (GHC.srcSpanStart a `compare` GHC.srcSpanStart b)
@@ -1632,21 +1729,77 @@ spans :: SrcSpan -> (Int,Int) -> Bool
 spans span (l,c) = GHC.srcSpanStart span <= loc && loc <= GHC.srcSpanEnd span
    where loc = GHC.mkSrcLoc (GHC.srcSpanFile span) l c
 
+-- for now, use ANSI bold on Unixy systems.  On Windows, we add a line
+-- of carets under the active expression instead.  The Windows console
+-- doesn't support ANSI escape sequences, and most Unix terminals
+-- (including xterm) do, so this is a reasonable guess until we have a
+-- proper termcap/terminfo library.
+#if !defined(mingw32_TARGET_OS)
+do_bold = True
+#else
+do_bold = False
+#endif
+
 start_bold = BS.pack "\ESC[1m"
 end_bold   = BS.pack "\ESC[0m"
 
 listCmd :: String -> GHCi ()
-listCmd str = do
+listCmd "" = do
    mb_span <- getCurrentBreakSpan
    case mb_span of
       Nothing  -> printForUser $ text "not stopped at a breakpoint; nothing to list"
-      Just span -> io $ listAround span True
+      Just span | GHC.isGoodSrcSpan span -> io $ listAround span True
+                | otherwise              -> printForUser $ text "unable to list source for" <+> ppr span
+listCmd str = list2 (words str)
+
+list2 [arg] | all isDigit arg = do
+    session <- getSession
+    (toplevel, _) <- io $ GHC.getContext session 
+    case toplevel of
+        [] -> io $ putStrLn "No module to list"
+        (mod : _) -> listModuleLine mod (read arg)
+list2 [arg1,arg2] | looksLikeModuleName arg1, all isDigit arg2 = do
+        mod <- wantInterpretedModule arg1
+        listModuleLine mod (read arg2)
+list2 [arg] = do
+        wantNameFromInterpretedModule noCanDo arg $ \name -> do
+        let loc = GHC.srcSpanStart (GHC.nameSrcSpan name)
+        if GHC.isGoodSrcLoc loc
+               then do
+                  tickArray <- getTickArray (GHC.nameModule name)
+                  let mb_span = findBreakByCoord (Just (GHC.srcLocFile loc))
+                                        (GHC.srcLocLine loc, GHC.srcLocCol loc)
+                                        tickArray
+                  case mb_span of
+                    Nothing       -> io $ listAround (GHC.srcLocSpan loc) False
+                    Just (_,span) -> io $ listAround span False
+               else
+                  noCanDo name $ text "can't find its location: " <>
+                                 ppr loc
+    where
+        noCanDo n why = printForUser $
+            text "cannot list source code for " <> ppr n <> text ": " <> why
+list2  _other = 
+        io $ putStrLn "syntax:  :list [<line> | <module> <line> | <identifier>]"
+
+listModuleLine :: Module -> Int -> GHCi ()
+listModuleLine modl line = do
+   session <- getSession
+   graph <- io (GHC.getModuleGraph session)
+   let this = filter ((== modl) . GHC.ms_mod) graph
+   case this of
+     [] -> panic "listModuleLine"
+     summ:_ -> do
+           let filename = fromJust (ml_hs_file (GHC.ms_location summ))
+               loc = GHC.mkSrcLoc (mkFastString (filename)) line 0
+           io $ listAround (GHC.srcLocSpan loc) False
 
 -- | list a section of a source file around a particular SrcSpan.
 -- If the highlight flag is True, also highlight the span using
 -- start_bold/end_bold.
 listAround span do_highlight = do
-      contents <- BS.readFile (unpackFS file)
+      pwd      <- getEnv "PWD" 
+      contents <- BS.readFile (pwd </> unpackFS file)
       let 
           lines = BS.split '\n' contents
           these_lines = take (line2 - line1 + 1 + pad_before + pad_after) $ 
@@ -1672,7 +1825,10 @@ listAround span do_highlight = do
                    | otherwise  = 1
         pad_after = 1
 
-        highlight no line
+        highlight | do_bold   = highlight_bold
+                  | otherwise = highlight_carets
+
+        highlight_bold no line
           | no == line1 && no == line2
           = let (a,r) = BS.splitAt col1 line
                 (b,c) = BS.splitAt (col2-col1) r
@@ -1686,6 +1842,20 @@ listAround span do_highlight = do
             BS.concat [a, end_bold, b]
           | otherwise   = line
 
+        highlight_carets no line
+          | no == line1 && no == line2
+          = BS.concat [line, nl, indent, BS.replicate col1 ' ',
+                                         BS.replicate (col2-col1) '^']
+          | no == line1
+          = BS.concat [line, nl, indent, BS.replicate col1 ' ',
+                                         BS.replicate (BS.length line-col1) '^']
+          | no == line2
+          = BS.concat [line, nl, indent, BS.replicate col2 '^']
+          | otherwise   = line
+         where
+           indent = BS.pack "   "
+           nl = BS.singleton '\n'
+
 -- --------------------------------------------------------------------------
 -- Tick arrays
 
@@ -1712,13 +1882,14 @@ mkTickArray ticks
         [ (line, (nm,span)) | (nm,span) <- ticks,
                               line <- srcSpanLines span ]
     where
-        max_line = maximum (map GHC.srcSpanEndLine (map snd ticks))
+        max_line = foldr max 0 (map GHC.srcSpanEndLine (map snd ticks))
         srcSpanLines span = [ GHC.srcSpanStartLine span .. 
                               GHC.srcSpanEndLine span ]
 
-lookupModule :: Session -> String -> GHCi Module
-lookupModule session modName
-   = io (GHC.findModule session (GHC.mkModuleName modName) Nothing)
+lookupModule :: String -> GHCi Module
+lookupModule modName
+   = do session <- getSession 
+        io (GHC.findModule session (GHC.mkModuleName modName) Nothing)
 
 -- don't reset the counter back to zero?
 discardActiveBreakPoints :: GHCi ()