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65 lines
2.3 KiB
Plaintext
65 lines
2.3 KiB
Plaintext
What is REXX ?
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==============
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REXX is a programming language designed by Michael Cowlishaw
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of IBM UK Laboratories. In his own words: "REXX is a
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procedural language that allows programs and algorithms to
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be written in a clear and structured way."
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REXX doesn't look that different from any other procedural
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language. Here's a simple REXX program:
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/* Count some numbers */
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say "Counting..."
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do i = 1 to 10
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say "Number" i
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end
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What makes REXX different from most other languages is that
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it is also designed to be used as a macro language by
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arbitrary application programs. The idea is that
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application developers don't have to design their own macro
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languages and interpreters. Instead they use REXX as the
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macro language and support the REXX programming interface.
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If a REXX macro comes across an expression or function call
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that it cannot resolve, it can ask the application to handle
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it instead. The application only has to support the
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features that are specific to it, freeing the developer from
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handling the mundane (and time-consuming) task of writing a
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language interpreter. And if all applications use REXX as
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their macro language, the user only has to learn one
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language instead of a dozen.
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Differences between TRL (The REXX Language) and REXX/imc
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========================================================
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The following are all nonstandard features of REXX-imc
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* Rejection of labels ending with dot (in case of confusion between
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function.(args) and stem.(tail))
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* Compound variable accesses of the form "stem.'string constant'" and
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stem.(expression)
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* Acceptance of any non-zero number for logical truth, rather than just 1
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* "SAYN expression" to output lines without carriage return
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* "SELECT expression" to switch on a value
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* "END SELECT"
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* "PARSE VALUE" with multiple strings separated by commas
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* "PROCEDURE HIDE"
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* The following functions: chdir getcwd getenv putenv system userid
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plus these I/O functions: open close fdopen popen pclose fileno ftell
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* error messages 80-210, -1 and -3.
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Good sources of REXX information on the web:
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============================================
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REXX/imc Home page
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http://www.comlab.ox.ac.uk/oucl/users/ian.collier/Rexx/index.html
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IBM's REXX Language Page
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http://rexx.hursley.ibm.com/rexx/
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REXX Tutorials Page
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http://www2.hursley.ibm.com/rexxtut/
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