Right from the moment that a programmer downloads REBOL, it is obvious that REBOL is not like other programming languages. REBOL (which stands for the Relative Expression-Based Object Language and is pronounced as in “rebel without a clause) is not a massive, all encompassing programming language, instead it introduces the idea of the REBOL dialect. These dialects enable a programmer to produce small project specific languages which are perfect for:
- business rules
- database applications
- thin client / two tier applications
It's therefore just a matter of downloading REBOL's GUI (Graphical User Interface) and seeing exactly how flexible it is.
Obtaining REBOL
The hardest part of the process of installing REBOL is deciding which version to download. That's because there's:
- the free standard light GUI
- the more heavy duty (but still free) server version
- the software developer's kit (which is not free)
- the professionals' features (which, again, is not free)
However, to start with, the basic GUI is more than enough. And downloading it takes a matter of seconds (if that). That's because it's tiny. It's so small that the application developers don't even bother to compress it.
Getting Started with REBOL
Once the REBOL executable has been downloaded it should be placed in its own directory. That's because it will create a set of directories and files when it's first run (and that's done by double clicking on it). It will also request user details (as shown in figure 1 at the bottom of this article).
At this point it may be useful to be connected to the Internet because REBOL will try to download any access and the user will have access to documentation and example scripts. However, that's not necessary for the programmer to start working with REBOL.
A Simple REBOL Script
The process for creating a new script is quite simple:
- The programmer should start by clicking on the Local folder. This is where they will store any new scripts
- The Local folder will contain only one file at this point (as shown in figure 2). The programmer should open this file (entitled “Info”)
- Info.txt will open and the programmer should click on “New” and then “Save-As”. This new script should be saved with a “.r” file extension (for example “HelloWorld.r”), and this should be saved into the “Local” sub-directory
The script is now ready for the obligatory “Hello World” example. Every ROBOL script requires a ROBOL header. This can be empty:
Or it may contain more useful information:
The code is very simple:
This code is run by using Control-E and will:
- open a REBOL console window
- display the text
- pause for 5 seconds
- close the console window
However, if the programmer closes this script they will find that it doesn't appear in the REBOL Viewtop (the GUI dispplay) – even if they refresh it.
Adding a Script to the REBOL Viewtop
A script is added to the REBOL's Local section of the Viewtop by editing its index file:
- right mouse clicking on the Local folder image
- click on “Edit”
A references for the new script can now be added:
Once the index file has been saved and closed, and the Viewtop refreshed then the script will be visible to the programmer (as shown in figure 3). They will then be able to run the file (by clicking on it) or edit it (by left clicking on it). And the next stage is, of course, to move on to what REBOL is really good at - creating business rules with its dialects. That's discussed in How to Create a REBOL Dialect.
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