Re: scope and/or parameters (beginner)

[czgrr <czgrr@my-dejanews.com>]

In article <370b0c99.1137352783@news.dsuper.net>,
  fluffy_doo@dsuper.net wrote:
> On Mon, 05 Apr 1999 05:04:25 +0000, Corey Ashford
[snip]
> This exercise, in part learning to use "named" instead of "positional"
> association, has allowed me to realize the following, I think :
>
> 	The fact that a sub-program is declared INSIDE another, as
> 	opposed to OUTSIDE of it, makes no difference from the point of
> 	view of the compiler.  As long as any call to a sub-program is
> 	made AFTER its declaration it is treated exactly the same way.
>
> TRUE / FALSE ?
The short answer:

For the usage you gave in your original message, yes it makes no difference.


The long answer, part 1:

It does make one important difference. In the same way as local variables are
not accessible outside the routine they are declared in, declaring a routine
inside another limits the scope (accessibility) of that routine.

An example. In the message you originally wrote, you make a call:

>    One_Procedure
> 	(Second_Variable => Var_2, Third_Variable => Var_3);

but if you tried to make the following call *in the same place*:

>    Internal_Procedure ( One_Variable => Var_3 );

it would not compile. If you wanted "Internal_Procedure" to be available in
the same places as "One_Procedure", you would have to declare it outside
"One_Procedure".


The long answer, part 2:

This business about calling something after its declaration, strictly, is
true. But in the sense I felt you were talking about it here, you could have
structured your code this way...

> PROCEDURE One_Procedure
> 	   (	Second_Variable :	IN   The_Type;
> 		Third_Variable :	OUT  The_Type ) IS
> --  sub-programs: none ================================
> BEGIN -- One_Procedure
> 	Internal_Procedure ( One_Variable => (QUESTION) );
> END One_Procedure;
>
> PROCEDURE Internal_Procedure
> 	( One_Variable : IN OUT  The_Type ) IS
> BEGIN
> 	One_Variable := One_Variable + A_Constant;
> END Internal_Procedure;

and still have been able to get this to compile. What you do is to put a
declaration for "Internal_Procedure" before that for "One_Procedure", of this
form:

> PROCEDURE Internal_Procedure
> 	( One_Variable : IN OUT  The_Type ) ;  -- NOTE the semi-colon

Then you can call "Internal_Procedure" at any point after this, irrespective
of where the actual code for it lies.

Of course, if you have written specs and bodies, this is exactly the same as a
declaration in the spec - you can think of a spec as coming "before" anything
in the body, and so you can call anything in a package's spec from anywhere
within that package.

Phew! Some more things to play with, eh?

HTH, czgrr.

--
My opinions, etc, are not necessarily those of my employer.
They might not even be right.

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