Difference between REXX and CLIST

[Anks]

Dear All,

REXX and CLIST are two command languages available in TSO/E.

Can anyone tell what are the basic differences between them.
Like which are the features that are available in one and absent in other.

Moreover points to keep in mind while deciding which one to go for if i m writing new program.

Thanks
Anks

 

[rexxhead]

CLIST is supported on TSO; REXX is supported on TSO, VM/CMS, Unix, Sun, AS/400, Amiga, Commodore, etc. If there's any chance this will ever run on a different platform, go for REXX.

CLIST provides integer arithmetic; REXX provides floating point arithmetic. If you need to do anything more complicated than add, subtract, multiply, and divide, go for REXX.

CLIST subroutines are klutzy to implement; REXX is a full-featured block-structured procedural language.

The CLIST I/O model is one record at a time (and handle your own ENDFILEs); REXX uses EXECIO which permits you to load an entire array or queue with one operation.

There is one CLIST Language Reference Manual; the available REXX books and manuals require a pickup truck to move (unless you use the CD).

CLIST parameter-parsing beats REXX hands down. Certain TSO functions (like TEST) cannot be run from REXX.

ISPF table operations, especially TBDISPL, run faster (but not necessarily MUCH faster) in CLIST.



Frank Clarke
Tampa Area REXX Programmers' Alliance
REXX Language Assn Listmaster

 

[TampaScorpion]

Frank,
Knowing how much you like REXX, I am glad to see you give CLIST it's credit, and pointing out some of the weakness of REXX.

As I am sure that people can see REXX is generally the best way to go, especially if they have an example of each type to contrast and compare.

-J.D. Hill
Tampa Area REXX Programmers' Alliance

 

[kevinf2349]

Just to add one more advantage that REXX has over CLIST. REXX can be compiled, CLIST is always interpretive.

Compiling the REXX code gives you 'faster' code and of course you can hide the source code away making REXX better if you are writing to sell.

I believe that some restrictions apply to the REXX code that can be compiled (ie you are not allowed to use INTERPRET) but there is usually another way of getting the same result.

IMHO REXX is a lot easier to learn and it far more intuitive...and this from someone who spent more than 15 years using CLIST.

 

[rexxhead]

For heavy users of ISPF table facilities, the REXX compiler is usually not an option. I have seen compiled REXX code run slower than its interpreted sister.


Frank Clarke
Tampa Area REXX Programmers' Alliance
REXX Language Assn Listmaster

 

[kevinf2349]

Frank,

Yep I can see how heavy usage of tables could lead to potential performance issues with compiled code, but I have never benchmarked it so I have no experience of it first hand. Do you have any idea at what point is becomes self-defeating when using tables?

 

[rexxhead]

Kevin -- I don't have good, solid numbers. Once upon a time a table which normally ran 2500-3000 rows suddenly went (overnight) to 20,000+ rows and performance went to hell in a handbasket.

I'm presently maintaining one particular table which is about 1200 rows and performance is brilliant. I have had larger tables which worked OK.

I suspect the point-of-no-return is somewhere near 6000 rows. That probably is dependent on the number of columns, too.


Frank Clarke
Tampa Area REXX Programmers' Alliance
REXX Language Assn Listmaster

 

[KiwiREXXDude]

Frank, you left out the most fun useage of REXX - ObjectREXX for Windows.

That rocks... unfortunately there is only 1 site in Australia which uses it.

 

[rexxhead]

But there's also Regina, the product of the fertile brain of Mark Hessling, another Strine. Find a link to it from the REXX Language Assn page:

http://www.rexxla.org

Frank Clarke
Tampa Area REXX Programmers' Alliance
REXX Language Assn Listmaster