CS 15-212: Fundamental Principles of Computer Science II

Outline

About MLWorks

The purpose of this document is to minimize the amount of time you spend wrestling with the peculiarities of the environment, as opposed to the more conceptual aspects of the assignments.

Documentation for MLWorks

• MLWorks User's Manual
• MLWorks Reference Manual
• MLWorks Release Notes

MLWorks at CMU

• Only available for Sun SPARCstations
• Available for Solaris operating systems:
• Solaris: /afs/andrew.cmu.edu/scs/cs/15-212-X/bin/mlworks
• Use Sparc-5 or UltraSparc workstations in Andrew clusters:

  Cluster	Sparcs
  WeH 5201	56
  Morewood Gardens	7
  Hunt Library 2nd Floor	6

• Use Sparc servers remotely by telnet sun4.andrew.cmu.edu

Using Emacs with MLWorks

• Add the following code to the .emacs file in your home directory:

      (setq
         load-path
         (cons "/afs/andrew.cmu.edu/scs/cs/15-212-X/lib/emacs/"
               load-path))
  
      (autoload 'mlworks-server "mlworks-server" "The MLWorks server" t)
      (autoload 'sml-mode "sml-mode" "Major mode for editing Standard ML programs."
                t)
  
      (setq auto-mode-alist (cons '("\\.sml$" . sml-mode) auto-mode-alist))
      

• This code is available at /afs/andrew.cmu.edu/scs/cs/15-212-X/lib/emacs/mlworks-server.el
• Type Meta-x mlworks-server to start the MLWorks server
• The server requires that Emacs be run on the same machine
• Use the sunos directory instead of solaris for SunOS workstations
• To use XEmacs with MLWorks, replace "mlworks-server" with "cmu-mlworks-server" in the second statement above

Starting MLWorks

• From a Sparc workstation in an Andrew cluster:
  /afs/andrew.cmu.edu/scs/cs/15-212-X/bin/mlworks &
• From any workstation running the X-window system:
  telnet sun4.andrew.cmu.edu
  Enter user id and password
  On your workstation:
  xhost + unixn.andrew.cmu.edu, where unixn is the server you were connected to.
  On the server:
  /afs/andrew.cmu.edu/scs/cs/15-212-X/bin/mlworks &
  
• Make a link to your local bin directory to save typing:
  ln -s /afs/andrew.cmu.edu/scs/cs/15-212-X/bin/mlworks ~/bin/mlworks
rehash
mlworks &
• Note: mlworks is a version of mlworks that automatically includes the SML Basis Library
  Parts of the Basis Library will be used in the assignments

The Podium

• Podium appears when MLWorks is starts up
• Text area shows "important" system messages
• Can't type into text area
• Can set preferences and bring up other tools
• Interrupt button suspends current computation

Preferences

• Mode Preferences
  • Choose SML '96
  • Turn off Optimizing while debugging
  • Turn on Debugging unless timing
• Editor Preferences
  • Choose Emacs Server
  • The User's Guide tells how to configure other editors
• General/Miscellaneous Preferences
  • Select all options here
  • Can turn off Use error browser to get in-line error messages
• Compiler Details
  • While debugging: turn on first set, turn off second set
  • For timing: turn off first set, turn on second set
• Language Details
  • Turn off all options here
• Save Preferences retains preferences for the next session
• Some preferences are only mentioned in the library documentation in the Reference Manual

The Listener

• An interactive dialogue with SML
• Text Area
  • Type expressions and declarations into text area
    Listener
    MLWorks> 3+4;
val it : int = 7
MLWorks> val seven = 7;
val seven : int = 7
  • MLWorks responds with type and value or error message
    MLWorks> fun inc n = n+1;
val inc : int -> int = fn
MLWorks> val bogus = nothing;
Close
    Line 1: error: Unbound value nothing
  • Expressions are implicitly bound to it
MLWorks> val pi = 3.14159;
val pi : real = 3.14159
  • Each item must be terminated by a semicolon
    MLWorks> val yes = true
... no response ...
    ;
val yes : bool = true
  • Multi-line items are allowed
    MLWorks>
fun factorial 0 = 1
| factorial n = n*(factorial (n-1));
val factorial : int -> int = fn
  • Tab completes declaration names
    MLWorks> fac Tab
    ;
  • Put cursor on a previous line to repeat it
  • Emacs key sequences are supported
• Buttons
  • Evaluate terminates current item
    MLWorks> factorial 10; Evaluate
    val it : int = 3628800
  • Step evaluates and invokes debugger
    MLWorks> factorial 3; Step
    Debugger window appears
    Step 4 times
    Abort
    val it : int = 6
  • Time evaluates and reports execution time
    MLWorks> factorial 10; Time
    val it : int = 3628800
0.06 (user: 0.04, system: 0.02, gc: 0.00)
  • Clear erases current item
    MLWorks> erase me Clear
    
  • Clear All erases text area
  • Abandon cancels current item without clearing it
    MLWorks> don't do this Abandon
    
  • Previous and Next step through history of prior items
• File menu
  • Save Source dumps all top-level declarations to a text file
    Save Source As...
    mystuff.sml
    OK
  • Use File... reads a source file into the top-level
    Use File...
    mystuff.sml
    OK
    val it : unit = ()
    ...
  • Use Use File... with an external editor to develop assignments
  • Other items are used for multi-file projects
• Edit menu
  • Use Copy and Paste to save typing
  • Paste is only enabled for terminal inertion point
  • Use Find... to locate library objects
    Find...
    Check all boxes stream
    Cancel
• View menu
  • Controls how values are printed
  • Can be used to look at contents of function values--
    useful with programming with higher-order functions
• Action menu operates on most recent function or value
• History menu provides random access to prior items

The Error Browser

• Appears when malformed program text is encountered
  -- Emacs --
  not a valid SML declaration
  Ctrl-x Ctrl-w badstuff.sml
  -- MLWorks --
  Use File... badstuff.sml
  Close
  Line 1: error: Unbound value a
• Can report syntax errors or type errors
  -- Emacs --
  val invalid = false+4
  Ctrl-x Ctrl-s
  -- MLWorks --
  Use File... badstuff.sml
  Close
  Line 1: error: Function applied to argument of wrong type
• Upper pane lists errors for a given item
  Lower pane provides details
• Double-click list item to select erroneous text in Emacs
  Use File... badstuff.sml
  Double-click Line 1: ...
  
• Redo recompiles code after a fix
  -- Emacs --
  val valid = 3+4
  Ctrl-x Ctrl-s
  -- MLWorks --
  Redo
  val valid : int = 7
• Can be turned off to get traditional error messages
  Uncheck Use error browser in General Preferences

The Inspector

• Shows the type and contents of values in detail
  MLWorks> (true, "wombat", [[1], [1+1, 2], [1+1+1, 1+2, 3]]);
val it : (bool * string * int list list) = (true, "wombat", [[1], [2, 2], [3, 3, 3]])
Inspect
  
• Remembers original source code for a given value
  Notice that the strings in Source and Value are different
• Double-click items in Components area to show their structure
  Double-click (true, "\...", [...])
  Double-click [[...], [...], [...]]
  
• Auto Selection inspects each value as it is entered into the Listener
  Auto Selection
  MLWorks> (1, "two", 3.0);
val it : (int * string * real) = (1, "two", 3.0)
Double-click (1, "\...", 3.0)
  Close
• View menu controls how values are displayed

The Context Browser and The System Browser

• Context Browser shows declarations that you have entered, plus the SML Basis Library
  Context Browser
• System Browser shows declarations that are provided by MLWorks
  System Browser
• Behavior of browsers is otherwise identical
• Context Browser is a good way to find library declarations
  Context Browser
  Double-click Math
  Double-click String
  Double-click TextIO
• Selection field saves typing for nested structure components
  Click val output: (outstream * string) -> unit
  Double-click Selection field
  Copy
  MLWorks> Paste ;
val it : (TextIO.StreamIO.outstream ref * string) -> unit = fn
• Inspect opens the Inspector on a selected declaration
• Filters... controls which kinds of declarations are displayed
• System Browser is a good way to find pervasive identifiers

The Stack Browser (Debugger)

• Turn on debugging and turn off optimization before using the Debugger
• Appears when a run-time error occurs, or when a breakpoint is encountered
  MLWorks> hd []:int list;
  Abort
• Error Browser reports compile-time errors;
  Stack Browser reports run-time errors
  MLWorks> 1 div false;
  Close
  Line 1: error: Function applied to argument of wrong type
MLWorks> 1 div 0;
  Abort
• Compile-time errors are more common in SML and are usually easier to fix
• Top-most field shows reason for halt
  MLWorks> fun divide(n, m) = n div m;
val divide : (int * int) -> int = fn
MLWorks> fun badnews q = divide(q, 0);
val badnews : int -> int = fn
MLWorks> badnews 11;
• Local variables shows variables in scope of suspended functions
• Stack (grows upwards) shows suspended functions
• Select items in Stack to change items in Local variables
  Click badnews 11
  
• Abort aborts the computation in progress
  Abort
• Continue resumes the computation in progress
• Step continues for one function call
• Next continues until the current function returns
• Continue, Step, and Next are only enabled for breakpoints

The Breakpoint Manager and The Trace Manager

• Breakpoint Manager is a list of functions that will invoke the debugger
  Breakpoint Manager
  OK
• Trace Manager is a list of functions that will trace their execution
  MLWorks> divide;
val it : (int * int) -> int = fn
Trace
  Trace Manager
  OK
  MLWorks> divide(47, 11);
divide (47, 11)
divide returns 4
val it : int = 4
MLWorks> divide;
val it : (int * int) -> int = fn
Untrace
• Behavior of managers is otherwise identical
• Add Name adds a function to the breakpoint/trace list
  Breakpoint Manager
  divide
  Add Name
  OK
  MLWorks> divide(47, 11);
  Continue
  val it : int = 4
• Delete Name removes a function from the breakpoint/trace list
  Breakpoint Manager
  divide
  Delete Name
  Doesn't seem to work...
• Delete All disables breakpoints/tracing for all functions
  Delete All
  OK

The History Window

• History Window is a list of all declarations that have been seen accepted by any Listener
  History
• Note that the SML Basis Library is also visible here
• Remove Duplicates deletes all declarations that have been shadowed by new declarations
  Remove Duplicates