Code: third_year_project/calc/Calculator.ajava

Abstract: A project investigating and developing an implicitly concurrent programming language, based on a metaphor taken from the physical world is reported. Uses a programming paradigm where programs consist of systems of autonomous agents, or active objects which communicate via message passing. A language enhancing Java with actors and linear types is presented. Example programs are written, compiled, and executed to evaluate the usefulness of the language. The language found to provide a familiar notation for implicit parallelism, and a compelling new model for concurrency, combining the performance of shared variables with the elegance of message passing.

import javax.swing.*;
import java.awt.*;

public aclass Calculator extends AFrame {

    // members   
    final ALU alu;
    final NumberBox display;
    final ADigitPad digitPad;
    final AOpPad opPad;
    
    // constructor
    public Calculator() {
        super("Calculator");
        frame.setSize(300, 200);
        this <-- new SetCloseOperation(SetCloseOperation.EXIT_ON_CLOSE);
        
        // alu
        alu = new ALU();
        
        // create panel
        APanel panel = new APanel();
        contentPane <-- new AContainer.AddComponent(panel);
        
        // number display
        display = new NumberBox();
        display.OnOperation <-- new Event.Subscribe(alu);
        alu.OnResult <-- new Event.Subscribe(display);
        panel <-- new AContainer.AddComponent(display);
                
        // create digit pad
        digitPad = new ADigitPad();
        digitPad.OnClick <-- new Event.Subscribe(display);
        panel <-- new AContainer.AddComponent(digitPad);
        
        // create operation buttons
        opPad = new AOpPad();
        opPad.OnClick <-- new Event.Subscribe(this);
        panel <-- new AContainer.AddComponent(opPad);

        // register for key presses
        OnKeyTyped <-- new Event.Subscribe(this);
        digitPad.OnKeyTyped <-- new Event.Subscribe(this);
        opPad.OnKeyTyped <-- new Event.Subscribe(this);
    }
    
    // receives an operation command
    public react (char op) {
        if (validOperator(op)) {
            display <-- new Operation(op);
        }
    }
    
    // key press
    public react (KeyboardEvent e) {
        // numeric digit
        if (Character.isDigit(e.character) || e.character == '.') {
            display <-- e.character;
        }
        // return
        else if (e.character == '\r' || e.character == '\n')
            this('=');
        // operator
        else this(e.character);
    }
    
    // operations
    public class Operation {   
        public char operator; // operation to perform
        public double operand; // value of number register when op is pressed
        public Operation(char op) {
            this.operator = op;
        }
    }
    
    private static boolean validOperator(char c) {
        switch (c) {
            case '+': case '-': 
            case '*': case '/':
            case '^': case '=':
                return true;
            default: 
                return false;
        }
    }
}

ActiveJava

Calculator.ajava