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Pete Dashwood  
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 More options Jul 29 2012, 8:14 pm
Newsgroups: comp.lang.fortran, comp.lang.pl1, comp.lang.cobol
From: "Pete Dashwood" <dashw...@removethis.enternet.co.nz>
Date: Mon, 30 Jul 2012 12:14:05 +1200
Local: Sun, Jul 29 2012 8:14 pm
Subject: Re: Reserved Words
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Richard Maine wrote:
> Pete Dashwood <dashw...@removethis.enternet.co.nz> wrote:

>> Robin Vowels wrote:

>>> When new keywords are introduced into the language, reserved words
>>> cause some existing programs to fail.

>> If you use a proper Editor with Intellisense (Visual Studio/Eclipse
>> are just 2 very good ones...) you will NEVER use a reserved word
>> improperly so that argument carries no weight for me.

> That might be so for limitted values of "never". It won't help the
> case where you have existing code and have to deal with a newer
> version of the language that adds new reserved words.

I take your point. Existing code MIGHT contain something which has now
become a reserved word.

But the first time you compile it, it will fail and that should prompt you
to run a Global edit.

>Even if the
> editor might help you find the problems in such code, revising large
> codes can be a major problem in environments where any revision
> necessitates revalidation. (In one project I worked on, revalidating
> the flight software costs about a million dollars).

Yes, regression testing is costly (not to mention tedious and time
consuming.)

>If one works only
> on programs that are of "modest" size and on which you are freely
> allowed to do global edits, one is likely to have trouble
> appreciating the environments where it is a big deal.

Robin, I have worked in such environments. One site I worked on had a COBOL
codebase of 60 million LOC (spread around 14 countries, but maintained from
one location). At the peak of our COBOL usage, PRIMA's Codebase was still
well under a million lines (today it is around 20,000 and decreasing), so
please don't think I don't understand the implications.

How "big a deal" it is will be determined by the site culture and approach.
A site where global edits are forbidden would be a worry. To me that conveys
lack of confidence in the people who are doing the maintenance. (They need
all the help they can get...restricting their use of tools and techniques
doesn't seem like a good thing to me, but again, it depends on the site
culture. You mentioned Flight software and I would agree that any software
where people's lives could be at stake requires more intense control than
might normally be required.)

I would want a Data Dictionary implemented on such a site and I would want
oto be able to ensure that every use of every dataname was documented,
cross-referenceable, and available as part of a generated data flow
analysis. That makes global editing a lot less intimidating.

>Sure, it is
> easy enough for one's own personal programs. I've done it with some
> of mine just because I preferred to avoid the confusion of a name
> conflict with a newly added intrinsic, even though my code could have
> continued working without the change. (SUM is certainly a variable
> name I used to use fairly often; there are others as well.)

Agreed.

Now consider it from the point of view of the compiler writer.

If there are NO reserved words how would you implement a language?

Pete.

--
"I used to write COBOL...now I can do anything."


 
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