A few comments.
1. It's best to avoid names that are, or are similar to, keywords.
2. There is a decades-long argument about NOVALUE. I am in the camp that
believes the default behavior to be too useful to give up; others believe
that it is dangerous.
3. The default environment for statements that are expressions is often an
application rater than the operating system, e.g., ISPEXEC, IISREDIT, XEDIT.
That behavior is incredibly useful.
--
Shmuel (Seymour J.) Metz
http://mason.gmu.edu/~smetz3
עַם יִשְׂרָאֵל חַי
נֵ֣צַח יִשְׂרָאֵ֔ל לֹ֥א יְשַׁקֵּ֖ר
________________________________________
From: IBM Mainframe Discussion List <[email protected]> on behalf of
Rony G. Flatscher <[email protected]>
Sent: Saturday, April 20, 2024 1:50 PM
To: [email protected]
Subject: Re: REXX vs other languages WAS: Rexx numeric digits and scientific
notation question
On 20.04.2024 17:40, Paul Gilmartin wrote:
> On Sat, 20 Apr 2024 11:08:03 -0400, Bob Bridges wrote:
>> It was while I was coding in REXX that I tried abutting a variable named 'x'
>> with another string, and couldn't figure out why the program behaved as it
>> did. Eventually figured out I had inadvertently created a hex constant.
>> Maybe as an overreaction, I have never since used one-character variable
>> names, always two or more. (What do I use for loop counters?, you ask. I
>> use 'j' plus another letter; 'jr' for records, for example, 'jd' for days
>> whatever. More obvious would have been 'i', but there are too many
>> two-letter reserved words even in REXX that start with 'i'.)
There are *no* reserved words in Rexx like in many other languages. (This
alleviates one to have to
learn them by heart. But more importantly, should the language get additional
keywords over time
they would not break existing Rexx programs that happen to use them already,
unlike other
programming languages.)
> I like to use longer names with mnemonic value as control variables and,
> if the body of the loop is more than a couple lines, cite the control
> variable at the END so the interpreter verifies nesting.
>
> Rexx is chaotic in context sensitivity of reserved words and in symbols'
> being evaluated almost everywhere with exceptions for e.g. ADDRESS.
There are no reserved keywords therefore it is interesting that you see
something chaotic there. But
maybe some of the fundamental Rexx rules are not really known or possibly
forgotten over time.
The Rexx rules are quite simple:
* everything outside of quotes gets uppercased,
o the content of quoted strings can be anything and never gets changed
(truly immutable),
* blanks around operators get removed,
* a blank between literals and symbols is the blank concatenation operator
* a symbol that was not assigned a value evaluates to the symbol itself (its
name which is the
uppercased string), otherwise it evaluates to its currently assigned value
The next step is to determine what kind of an instruction the resulting string
represents in order
to carry it out:
* if the second token is an equal sign then it is an assignment instruction
that gets carried out:
the expression right of the equal sign (RHS) gets evaluated and assigned to
the symbol (e.g.
ABC=3+4) to the left of the equal sign (LHS),
* if it is not an assignment instruction and the first symbol is a keyword
then it is a keyword
instruction that gets carried out,
* if it is neither then the resulting string is a command instruction which
gets handed over to
the operating system for execution, the command's return code can be
inspected immediately upon
return by using the Rexx variable RC (set by Rexx to make the return code
of the command
immediately available to the Rexx program).
The ADDRESS keyword instruction is just one of the keyword instructions of Rexx
which will allow to
control to which Rexx command handler the command instruction gets sent to
(among other things the
ADDRESS instruction allows to switch among different Rexx command handlers).
> Variable precision arithmetic is a boon. But there is no convenient
> library of elementary functions, probably the reason for the lack of
> elementary functions in Rexx.
This depends what functionalities you are missing/seeking. There are quite a
few Rexx function
libraries, many implemented in Assembler or C++.
If using ooRexx there is a free, open-source ooRexx-Java bridge available which
will make
immediately *all* Java class libraries there are and all their functionality
available to ooRexx,
really, all of them! The external function and class libraries in this case are
not implemented in
C++ or Assembler, but in Java. And Java has become *fast*, one of the fastest
languages there is.
If you look at Java and its standard runtime environment (JRE) you hardly miss
any functionality
there, from GUIs, to XML processing to secure Internet programming etc. E.g. if
you have a need to
transport data via SSL/TLS you get that infrastructure from the JRE for free at
your fingertips (on
all platforms) and can exploit it from Java, and with the ooRexx-Java bridge
installed also directly
from ooRexx.
Anyway, it is hard to conceive functionality that could not be made available
to Rexx/ooRexx one way
or the other.
---rony
--
--
__________________________________________________________________________________
Prof. Dr. Rony G. Flatscher
Department Wirtschaftsinformatik und Operations Management
Institut für Wirtschaftsinformatik und Gesellschaft
D2c 2.086
WU Wien
Welthandelsplatz 1
A-1020 Wien/Vienna, Austria/Europe
http://www.wu.ac.at/
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