Espresso! A small cup of Java

1. Espresso!A small cup of Java Erin Adelman - eca41@columbia.edu Aaron Bauman - abd54@columbia.edu Philip Coakley - pwc35@columbia.edu Joya Zuber - jaz49@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 Espresso! Programming Language

3. Key Features • Simple Espresso! Programming Language

4. Key Features • Simple • Educational Espresso! Programming Language

5. Key Features • Simple • Educational • Object-Oriented Espresso! Programming Language

6. Key Features • Simple • Educational • Object-Oriented • Portable Espresso! Programming Language

7. Key Features • Simple • Educational • Object-Oriented • Portable • Efficient Espresso! Programming Language

8. Key Features • Simple • Educational • Object-Oriented • Portable • Efficient • Scalable Espresso! Programming Language

9. card HelloWorld { print(“Hello World!”); } A Taste of Espresso!Hello, World! Espresso! Programming Language

10. A Taste of Espresso!Hello, World! Espresso! Programming Language

11. number Java double string Java String number array Javadouble[] string array Java String[] object array object TextBox Button CheckBox List Image Oval Rectangle A Taste of Espresso!Data Types and Objects Espresso! Programming Language

12. A Taste of Espresso!Program Structure card card_name { statement; statement; … statement; } Espresso! Programming Language

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(); Espresso! Programming Language

14. A Taste of Espresso!Array Declarations number[3] aaron = 5.4; : double[] aaron = new double[3]; for( int i=0; i<3; i++ ) aaron[i] = 5.4; Espresso! Programming Language

15. A Taste of Espresso!Assignments phil = phil + 5; joya = joya + “ is cool”; aaron[2] = 5; erin[0] = “Sneak”; myButton.setWidth(phil); Espresso! Programming Language

16. 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); myRectangle.setWidth(20); myRectangle.setHeight(20); print("Hello, World!", cx+10, cy+25); } 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) { g = getGraphics(); I2 = createImage(getWidth(), getHeight()); Graphics temp = I2.getGraphics(); temp.setColor(getBackground()); temp.fillRect(0, 0, getWidth(), getHeight()); temp.drawImage(img, 0, 0, this); temp.setColor(Color.white); … … A Taste of Espresso!Sample Program Espresso! Programming Language

17. A Taste of Espresso!Sample Program Espresso! Programming Language

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! Espresso! Programming Language

19. Espresso! Programming Language

20. 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. A Taste of Espresso!State public class myApplet extends applet { Declarations Initializations Execute Draw Actions } Espresso! Programming Language

21. 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); myRectangle.setHeight(20); print("Hello, World!", cx+10, cy+25); } A Taste of Espresso!State public class myApplet extends applet { Declarations Initializations Execute Draw Actions } Espresso! Programming Language

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. Espresso! Programming Language

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. Espresso! Programming Language

24. A Taste of Espresso!Runtime Library Definition Button::EspressoButtonRT(this){ void setText( String ) String getText( void ) void action ( void ) } Espresso! Programming Language

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! Espresso! Programming Language

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. Espresso! Programming Language

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 Espresso! Programming Language