1. Espresso! A small cup of Java
Erin Adelman -
Aaron Bauman -
Philip Coakley -
Joya Zuber -
CS4115 Programming Languages and Translators
Professor Stephen Edwards, December 2003

2. Espresso! Programming Language
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
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Espresso! Programming Language

3. Espresso! Programming Language
Key Features
Simple
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Espresso! Programming Language

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

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

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

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

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

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

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

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
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Espresso! Programming Language

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

16. A Taste of Espresso! Sample Program
Espresso! program (21 lines)
card HelloWorld {
Image baby;
baby.setSource( "
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);
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Espresso! Programming Language

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

19. Espresso! Programming Language
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Espresso! Programming Language

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 }
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Espresso! Programming Language

21. A Taste of Espresso! State
card HelloWorld {
Image baby;
baby.setSource(
"
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); }
public class myApplet extends applet {
Declarations
Initializations
Execute
Draw
Actions }
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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.
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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.
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Espresso! Programming Language

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

26. Espresso! Programming Language
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.
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Espresso! Programming Language

27. Espresso! Programming Language
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
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Espresso! Programming Language