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1991-10-20
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Enhancements in Personal REXX 3.0
Here is a summary of the major new features in Personal REXX 3.0:
* Performance
Many REXX programs will run significantly faster with Personal
REXX 3.0 than they did with Personal REXX 2.0 (which itself
was much faster than earlier versions). Some programs will run
more than twice as fast, and one beta tester reported that
parts of his application were more than 6 times as fast.
Areas which will show the greatest improvement include integer
arithmetic, simple loops, and some common character-string
functions (like RIGHT, LEFT, SUBSTR, WORD). However, almost
every program will exhibit a noticeable performance
improvement.
* Ability to run large applications
A swapping capability has been added that allows REXX programs
to invoke large applications like databases, spreadsheets, or
graphics with only about 2K bytes of overhead. In effect,
there is no longer any limitation due to the size of the REXX
language processor on the sorts of work you can do with REXX.
Swapping may be either to disk (including ramdisk) or EMS.
Control over when swapping is done and the location of the
swap file is provided by a new built-in function. For greatest
flexibility, defaults for the swap parameters can be provided
by a DOS environment variable.
* Compatibility
Personal REXX 3.0 is compatible with MS-DOS and PC-DOS 5.0.
It is also compatible in both language and built-in functions
with IBM's OS/2 (Release 1.3) REXX implementation. Programs
written for the IBM REXX which do not use OS/2-specific
features should, in most cases, run unmodified in DOS with
Personal REXX. (DOS memory limitations may place restrictions
on program size.)
* New REXX language features
Personal REXX now supports the most recent REXX language
features, as described in the second edition of Mike
Cowlishaw's The REXX Language. (This reference is included in
the upgrade package, but may be omitted for a slight saving
of cost.) The new features include:
- The VALUE function can now set variables as well as
retrieve their values (eliminating the need to use the
INTERPRET instruction in many cases). It can also
retrieve and set values of DOS environment variables.
- A list of variables can be supplied to EXPOSE as the
value of another variable, making it much easier to
expose variables that need to be globally available
throughout a program.
- Variables can now be used in PARSE templates for
positional patterns. That is, variables can be used to
specify absolute or relative column numbers.
- A NOTREADY condition has been implemented to allow
handling of I/O errors. A STREAM built-in function has
been added to perform certain kinds of I/O operations.
- Handlers for the ERROR, FAILURE, HALT, and NOTREADY
conditions can be invoked by CALL as well as SIGNAL. This
makes it possible to return to the point of error after
processing the condition. Several different handlers for
each type of condition can be provided in the same
program, since the label that identifies the handler no
longer needs to be the same as the name of the condition.
* New built-in functions
A number of additional built-in functions have been defined.
They provide new capabilities such as:
- syntax checking of file names, and identification of
device and directory names
- changing the time/date stamp on a file
- saving and restoring all environment variables, and
determination of the total size and free space available
in the DOS environment
* More flexible use of resident programs
The REXX "Interrupt Manager" is no longer required if one
doesn't need the services it enables. All Personal REXX
resident programs can be unloaded when they are not needed.
* Licensed run-time version available
A version of the REXX language processor that is capable of
running previously compiled Personal REXX programs has been
created. It cannot by itself execute uncompiled programs.
The run-time module is not included with the standard Personal
REXX retail package or the 3.0 upgrade package. Instead, it
will be provided under the terms of a special license from
Quercus Systems for a specified number of copies. This license
permits software developers to distribute the run-time module
and any necessary Personal REXX utilities with their
applications, without requiring end users to pay for a
complete Personal REXX package.