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From: "Kevin Wilson" <Kevin.Wilson@konstanz.netsurf.de>
Subject: Use of constants on EFA
Date: 1997/11/05
Message-ID: <63qkmc$8va$1@uttwil.bodensee.com>#1/1
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Organization: ISC Konstanz, Germany
Newsgroups: comp.lang.ada
Date: 1997-11-05T00:00:00+00:00
List-Id: <comp.lang.ada>


For Eurofighter software we must conform to the following coding
standards :

EF Software Programmer's Manual PL-J-019-V-1101 Issue 4 April 1992
which contains a section saying :

5.4.2.1 Constants
Objects shall be defined as being constant if their value is fixed
throughout the execution of the software.

As would be expected we have taken this to mean that if a variable is fixed
within its scope (whatever this may be) then it should be a constant.

So for example

    declare
      Status : constant Status_Type := Get_Status ;
    begin
      if Status = Good
      then
        Do_This ;
      else
        Do_That ;
      end if ;
    end ;

would be OK.

However our customer (who must accept our code) states that constants
should only be declared at package level. They argue that in the
above example the constant will change its value if the code is executed
again, therefore is not fixed !

Apart from the question of good programming practice, we rely heavily
on declaring local constants to read unconstrained array structures
returned by functions and without this would require untidy interfaces
and I would imagine more memory.

Any comments on this would be appreciated or if there are any people
reading this who were involved in the writing of this document and can
clarify what was meant by this statement please let me know.

K.Wilson