The NetRexx Tutorial - Preface

Preface

Introduction.

This book is addressed to both professional programmers and end users who want to learn more about the NetRexx language.

NOTE: The following documentation refers to NetRexx version 1.00 and following.

 
 *** This section is: 
  
 *** and will be available in next releases

When to use NetRexx.

This topic is likely to be a source of endless arguments (both pro and con).

This is my genuine opinion.

PROs:

• NetRexx is very easy to read. You can practically program in English (1)
• there is only ONE NetRexx native data type (the string);
• there is almost no need for special characters (like delimiters, identifiers, etc);
• NetRexx has very powerful features, such as arbitrary numeric precision, parsing, easy string handling, etc.
• NetRexx is not tailored to a particular operating system; the very same code can run on:
  • Windows 95/NT (TM),
  • UNIX (TM) (eg. AIX (TM), HP/UX (TM), IRIX (TM), SunOS (TM), Solaris (TM), etc.),
  • OS/2 (TM),
  • Macintosh (TM),
  In fact NetRexx will run on any platform that supplies a Java Virtual Machine (JVM) (TM) (more on this later.
• If you are (or were) a FORTRAN, PL/I or PASCAL programmer you will probably find NetRexx closer to your 'way-of-programming' than any other language available for the JVM. NetRexx eases the transition for programmers familiar with "procedural" languages into the object oriented paradigm.

CONs:

• NetRexx is not ( or at least not exactly) Rexx, so Rexx (or Object Rexx) fans will be faced with a "transition period". You cannot get your Rexx code immediately running in NetRexx (as you can do with Object Rexx) unless it is a very simple program.
• NetRexx compiles your program into Java byte-code. The code is then very much slower, in terms of execution, than a native Object Rexx or "classic" Rexx. I've measured up to a order of magnitude slower. This performance problem is due to the Java byte-code running in the JVM and is not an inherant problem with NetRexx; raw Java code is just as slow!

About the examples in this book.

>From the very first chapters, I will present and discuss some 'real' NetRexx program atoms (i.e. code fragments (usually methods) ) that you can use in your programs after having learnt the language.

I have noticed that many 'user guides' present as examples, programs you will probably never use again in your life; in fact these programs are often totally useless, brought into existence only so that the author can show particular features of the language involved.

I prefer to give you something 'real'; program atoms you can insert in your code, or programs you can run and use even after having finished with this book. The obvious disadvantage in such an approach is that some constructs may not be entirely clear, since they will only be explained several chapters further on. Please be patient, and do not be concerned about things that, at a particular point in your progress through the book, are not completely understood. You can always come back to them later.

 
 *** This section is: 
  
 *** and will be available in next releases

Book structure

This book is divided into four parts.

 

Part One
   (Writing simple programs)

   - Basic Concepts
   - Introduction to NetRexx
   - Language Basics
   - Operations on Numbers
   - Operations on Strings
   - Control Structures

Part Two
   (Object Oriented Programming)

   - Objects, Classes and Interfaces
   - Operations on files
   - Sockets and Networking
   - System Interface
   - Threads
   - Database Operations

Part Three
   (Interfacing with the WEB)

   - Applets
   - Graphical Interfaces
   - Advanced Graphics

Part Four
   (Advanced topics)

   - Additional Instructions
   - More on Algorithms
   - NetRexx for Rexxers
   - Tools
   - Miscellaneous

 

Conventions.

In order to be consistent, a 'standard' is being followed in presenting the various code samples and running examples.

When I show a full program example, the code appears like this:

+----------------------------------------------------------------------+ | /* |01 | * Code example |02 | */ |03 | say |04 | say 'This is a code example' |05 | say |06 | exit 0 |07 +----------------------------------------------------------------------+ codeex.nrx

Line numbers may be used in comments related to the code. You will find the file id at the bottom right-hand corner of the code, making it easier to find the referenced portion of the code if you already have the sample code on your computer.

When referring to only a small piece of a program, the code appears like this:

 
------------------------------------------------------
if test then
  do
    say 'Running in test mode.'
  end
------------------------------------------------------
                                            if example
 

Example sessions are presented like this:

....................................................................
rsl3pm1 (201) codeex

test

rsl3pm1 (202) ls -la codeex
-rw-r--r--   1 marchesi system        50 Jan 24 20:03 codeex
rsl3pm1 (203) 
....................................................................
                                                               outex

What you should type is written in bold characters. The rsl3pm1 (NNN) prompts are simply those of the machine from which sample sessions were taken, so just ignore them.

Syntax examples appear as:

 

   rc = socket('VERSION')

 

with the method invocation in bold characters, and the arguments in italics.

Data File Samples appear as:

+------------------------------------------------------------------+
| data file                                                        |
| sample                                                           |
+------------------------------------------------------------------+
                                                         sample.DATA

with, again, the file id at the bottom right-hand corner.

Acknowledments

Several reviewers have helped, by questions and comments, to clarify the aims and exposition of the book. Mark Hessling was extremely helpful in reading the preliminary version of the book, which was typeset using his XEDIT-like text editor; THE.

Many thanks also to Bernard Antoine and David Asbury of the CERN CN division for their help and suggestions.

Summary

Let us now make a resume' of what we have seen so far in this chapter.

 
 *** This section is: 
  
 *** and will be available in next releases

File: nr_2.html.

Last update was done on 18 May 1998 21:47:33(GMT +2).