Electric Communities: E Programming Language

Hello World


This first tutorial provides annotated code for the familiar Hello World application. This introductory application introduces you to basic E concepts:


Hello World

To run this tutorial, enter the following code and study the walkthrough that accompanies it. This example is also available in the online example suite as HelloE.e.

/*

HelloE.e Introductory hello world application to demonstrate E basics. Copyright Electric Communities */

public class HelloE { public static void main(String args[]) { HelloWorld first = new HelloWorld(); first <- hello(); } }

eclass HelloWorld { emethod hello() { System.out.println("Hello World"); } }


The Walkthrough

E-objects function by sending messages to one another, and operate optimistically. Messages can have parameters, just like a regular Java method call. When Object A communicates with Object B, Object A sends a message through the Channel to Object B. Object B would have the proper E-code to handle that message.

When run, the code executes in the following order:

  1. main instantiates the E-object first, an instance of the E-class HelloWorld.
  2. main sends the message hello to first.
  3. first executes the HelloWorld E-method hello to handle the message.
  4. hello prints out, ``Hello World''.


Compiling and Running

To compile source code for the E runtime, use the ecomp compiler:

  ecomp filename

The ecomp command compiles E and Java source files directly into Java bytecodes. You can then run your compiled program with the E Java interpreter (the javaec command):

  javaec filename

For more information on these commands, see the E Tools and Utilities section in the E Programmer's Guide.


Copyright (c) 1996 Electric Communities. All rights reserved worldwide.
Most recent update: 5/29/96