Re: Simplest way to protect a variable ?

[Ted Dennison<dennison@telepath.com>]

In article <9n9r4c$srt$1@snipp.uninett.no>, Reinert Korsnes says...
>Let's say I initiate a "global" variable, A (for example an array), by
>calling a procedure (which may read data from a file).  And I want to be
>sure that the content (value) of this variable is not changed by
>another procedure.  The variable is "global" in the sense that it is 
>available in many many other routines.   

If I take the literal interpretation of what you are saying, you want one
routine to be able to set it once, and everyone else only having read-only
access.

The easiest way to do that is to declare it as a constant in its package spec.
If you need a function to initialize it, put the function in a package that
doesn't depend on your package's body, and do a pramga elaborate_all on its
package when you "with" it.

A more flexible way to do it is to put the global variable inside the package
body of the setter. For all the read-only clients, provide a function in the
package spec that returns the current value of the variable. Code in the package
body can now muck with your global at will, but no-one else can (unless you
provide them a routine to do so). Among other benifits, this allows you to
change the implementation of your "global" without affecting your read-only
clients.

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