Re: Optimising string handling in application

[Frode Tenneboe <ft@alne.edh.ericsson.se>]

tmoran@acm.org wrote:
>> Follow-up question: Is it safe to asume that strings _allways_
>> start with 'First = 1 (provided the (sub)type starts with 1) except when
>> passing slices where 'First = start_of_slice?
>   Luckily, you needn't assume anything.  There are specific rules about
> the value of 'first.  If those rules, in some particular case, don't
> *guarantee* that 'first=1, then you can't "assume" that 'first=1.

Bad phrasing of the question. I looked in RM 4.3.3 (Array aggregates)
for an answer, but I'm still not absolutely certain that my perception
of strings (or other array-types for that matter) is correct.

For subprograms which can accept unconstrained arrys (eg. String)
it is necessary to use 'First and friends. Is this the only case where
it is not guaranteed that 'First = 1?

Example:

   procedure Replace_Callsign_In_Msg
     (Msg             : in out Dpu_Loc_Messages.T_Msg_Data_Str;
      Msg_Length      : in out T_Integer_32;
      Callsign        : in     Dpu_Loc_Messages.T_Msg_Callsign;
      Callsign_Length : in     Positive) is

If I were to call this with:

   Replace_Callsign_In_Msg
     (Msg             => Loc_Insert_Msg.Data(2..Loc_Insert_Msg.Data'Last),
      Msg_Length      => Loc_Insert_Msg.Data_Length-1,
      Callsign        => Individual_Callsigns.Callsigns(I).Callsign,
      Callsign_Length => Individual_Callsigns.Callsigns(I).Length);

Can I assume that 'First of Msg inside Replace_Callsign_In_Msg =1?

Where in RM is this dealt with?

Regards,
 -Frode

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