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From: Stephen Leake <stephen.a.leake.1@gsfc.nasa.gov>
Newsgroups: comp.lang.ada
Subject: Re: package body functionality
Date: 29 May 2001 15:11:30 -0400
Organization: NASA Goddard Space Flight Center
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f97stdi@dd.chalmers.se (Staffan Dittmer) writes:

> the question might be a bit obscure but 
> considering the two package bodies below
> 
> package body A is
>  variable: some_type:=call_some_function_outside_A;
> end A;
> 
> package body B is
>  variable: some_type;
> begin
>  variable:=call_some_function_outside_B;
> end B;
> 
> I know that in B the variable will be assigned
> every time a program using the package is run,

This is seriously wrong! B.variable is _not_ set many times. It
would be interesting to understand how you got that impression.

B.variable will be set _once_, at "elaboration" time. Elaboration
happens just before the main Ada program is run. All packages in the
program are elaborated, in an order determined by the compiler.

Note that if a function is called before its package is elaborated,
the exception Program_Error is raised; this is before your main
program gets to start.

To be safe, package A should have a 'pragma Elaborate' for the package
containing 'some_function_outside_A', and similarly for B.

> 
> but is this also true for A, or will the variable in this case only
> be assigned at compile time ?

As for B, A.variable is set at elaboration time.

-- 
-- Stephe