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From: sommar@enea.se (Erland Sommarskog)
Newsgroups: comp.lang.misc
Subject: Re: SP as "no goto's and nice indentation"
Message-ID: <1977@enea.se>
Date: 8 Aug 90 20:23:37 GMT
References: <9007300920.AA20411@thep.lu.se> <429@e2big.mko.dec.com> <1961@enea.se>
Organization: Enea Data AB, Sweden
Lines: 39

(Did this one make it to the outer world? Some other I posted last
week didn't seem to. Apologies if you see this twice.)

Christopher Gillett (gillett@ceomax.dec.com) writes:
>Of course, I claim that global variables, like
>any good programming language construct, are wonderful things when used
>properly and in moderation.

Definitely. But very high moderation. My experience after having
programmed mainly in various modular Pascal dialects and some
Ada is:

* Never, NEVER, jamais, non mai, export a variable from one module
  to another. This will always beat you in the end.

* If you have a one-instance structure, for instance a table, it
  is very good to put it on global level in a module, only
  accessible through calls to that module.

* Sometimes you run in the situation that there are a set of
  parameters you just pass from routine to routine, giving
  all routines seven-eight parameters which is not so nice.
  One solution can be to bundle them in a record type, but
  sometimes putting some of them on global level in the module
  might be the solution. Typically parameters from the environment
  you read once are best handled this way.

Also:
  Declare a variable as close to the point where it used. If you
  can declare variables in blocks like in C or Ada do so. If your
  Pascal compiler allows arbitrary order of CONST, TYPE, VAR,
  FUNCTION/PROCEDURE by all means use it.

It has seldom, if ever, happend to me that I've read other someone
else's code and thought: "He uses too few global variables". But
the opposite is just to common. You see some constants, some type,
and then - wham! 30 global variables waiting for you.
-- 
Erland Sommarskog - ENEA Data, Stockholm - sommar@enea.se