Restructured Extended Executor

Restructured Extended Executor (REXX) is a language, initially R evised EX ecutor, but the Sigle was already deposited, was invented by Mike Cowlishaw , researcher of IBM. Language interpreted procedural, it is one of the only heirs to PL/I, or at least to the clear Syntaxe of the PL/I.

It is the language of Script more used on the Mainframe S of IBM, in particular VM/CMS , then later MVS/TSO .

It has an implementation Open Source, provided out of standard with certain distributions Linux. Interpreters REXX, as well commercial as Open source, are available on a vast range of platforms and Compilateur S are available for all the central processing units IBM.

Its syntax was conceived with an aim essential to facilitate the training and the second reading of the code.

Here for example a program REXX:

 C i=1 to 5
    yew i=3 then say " Trois" 
           else say I
 end

Its execution gives

1
2
Three
4
5

Principles

syntax very close to systematic PL/I
use of tiny (reading 30 % faster, according to its creator Mike Cowlishaw ;
character of useless end of line (except when one wants to separate several instructions on the same line);
not of reserved words;
not of {} nor of. The indexing is done by a not qualifying which allows the numerical indexing or by character string (hash). examples: service.3095 or anniversaire.patron;
not of pointers;
few necessary brackets;
intuitive grammar (see the example above);
conditional operations standards (C i=…, C forever, while/C and C until);
Management system of exceptions of a very simple use thanks to activation signal one… .
the instruction parse allows the decomposition of chains structured in their basic elements in a more readable way (but as less concise) as the regular expressions.

There exists a Rexx compiler which makes it possible to obtain at the same time more stable scripts in the case of a management by version, a faster execution, and a certain protection against the flight or the inopportune modifications of the source code.

Derived

REXX gave two evolutions different, but remained little used because incompatible between them:

NetREXX, directed network
Object REXX, directed object

Regina has more success: it is simply the version of REXX in Free software.

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