Espresso A small cup of Java

1
Espresso!A small cup of Java

• Erin Adelman - eca41_at_columbia.edu
• Aaron Bauman - abd54_at_columbia.edu
• Philip Coakley - pwc35_at_columbia.edu
• Joya Zuber - jaz49_at_columbia.edu
• CS4115 Programming Languages and Translators
• Professor Stephen Edwards, December 2003

2
Espresso! is

• A simple and efficient way for programmers of all
  levels to create java applets.
• An educational language to familiarize novice
  programmers with java syntax.
• Similar to Tcl and Java in syntax and semantics

3
Key Features

• Simple

4
Key Features

• Simple
• Educational

5
Key Features

• Simple
• Educational
• Object-Oriented

6
Key Features

• Simple
• Educational
• Object-Oriented
• Portable

7
Key Features

• Simple
• Educational
• Object-Oriented
• Portable
• Efficient

8
Key Features

• Simple
• Educational
• Object-Oriented
• Portable
• Efficient
• Scalable

9
A Taste of Espresso!Hello, World!

• card HelloWorld
• print(Hello World!)

10
A Taste of Espresso!Hello, World!
11
A Taste of Espresso!Data Types and Objects

• number
• Java double
• string
• Java String
• number array
• Java double
• string array
• Java String
• object array

• object
• TextBox
• Button
• CheckBox
• List
• Image
• Oval
• Rectangle

12
A Taste of Espresso!Program Structure

• card card_name
• statement
• statement
• statement

13
A Taste of Espresso!Type Declarations

• number phil 5
• double phil 5
• string joya Joya
• String joya Joya
• TextBox myTextBox
• EspressoTextBoxRT myTextBox new
  EspressoTextBoxRT()

14
A Taste of Espresso!Array Declarations

• number3 aaron 5.4
• double aaron new double3
• for( int i0 ilt3 i )
• aaroni 5.4

15
A Taste of Espresso!Assignments

• phil phil 5
• joya joya is cool
• aaron2 5
• erin0 Sneak
• myButton.setWidth(phil)

16
A Taste of Espresso!Sample Program

• Espresso! program (21 lines)
• card HelloWorld
• Image baby
• baby.setSource( "http//www.columbia.edu
  /adb54/baby.jpg")
• Oval myOval
• number cx 150
• number cy 90
• number cwidth 100
• number cheight 50
• myOval.setX(cx)
• myOval.setY(cy)
• myOval.setWidth(cwidth)
• myOval.setHeight(cheight)
• myOval.setColor(red)
• Rectangle myRectangle
• myRectangle.setX(cx 7)
• myRectangle.setY(cy 30)

• Java program (106 lines)
• import java.awt.
• import java.awt.event.
• import java.applet.
• import java.net.
• import java.util.
• public class HelloWorld extends Applet
  implements Runnable
• Image img
• Graphics g2 null
• Image I2
• int sx
• int sy
• public synchronized void paint(Graphics g)

17
A Taste of Espresso!Sample Program
18
A Taste of Espresso!Development

• Create and analyze sample applets with desired
  Espresso! functionality.
• Java applet control flow and event handling are
  confusing.
• How can we abstract this applet architecture from
  the user?
• A robust back end!

19
(No Transcript)
20
A Taste of Espresso!State

• The walker and Code Generation class work
  together to maintain 5 states
• Declaring
• Initializing
• Executing
• Drawing
• Action Listening
• Each state represents a section in the generated
  applet file.

public class myApplet extends applet
Declarations
Initializations
Execute
Draw
Actions

21
A Taste of Espresso!State

• card HelloWorld
• Image baby
• baby.setSource(
• "http//www.columbia.edu/adb54/baby.jpg")
• Oval myOval
• number cx 150
• number cy 90
• number cwidth 100
• number cheight 50
• myOval.setX(cx)
• myOval.setY(cy)
• myOval.setWidth(cwidth)
• myOval.setHeight(cheight)
• myOval.setColor(red)
• Rectangle myRectangle
• myRectangle.setX(cx 7)
• myRectangle.setY(cy 30)
• myRectangle.setWidth(20)

public class myApplet extends applet
Declarations
Initializations
Execute
Draw
Actions

22
A Taste of Espresso!Scope

• Think Globally
• Espresso! has a single scope
• Variables can be declared at any time in
  Espresso!, but will all be initialized globally
  in the generated Java file.

23
A Taste of Espresso!Runtime Library

• The Runtime Library includes a suite of wrapper
  classes that build AWT constructs.
• RTL definitions are loaded into a type table that
  is used to verify library semantics
• The library is fully expandable to support new
  user defined objects and functions.

24
A Taste of Espresso!Runtime Library Definition

• ButtonEspressoButtonRT(this)
• void setText( String )
• String getText( void )
• void action ( void )

25
A Taste of Espresso!Testing

• Build language elements one by one, testing as we
  go.
• Have others outside the team write Espresso
  programs.
• Espresso! is so simple even UBW majors and
  monkeys can use it!

26
Lessons Learned

• Start early!
• Modularity is important for simplicity and
  effective testing.
• It is difficult to accommodate four busy
  schedules.
• Espresso! requires a lot of caffeine.

27
Future Developments

• Expand the Runtime Library to include more object
  types and methods.
• Allow the Espresso! programmer some control over
  the Applet Layout Manager
• Add keywords to dictate the design of the
  generated parent website