Thu, 17 Jul 2003 03:13:14 +1200
At 2003-07-11 21:55 +0100 Friday, Nick Roberts wrote:
>At 2003-07-08 11:14 +0530 Tuesday, Apurva Shukla wrote:
>> I am a starter in Ada and need certain help regarding arrays. I
>> have got a code in which there is a line which says:
>> a(11..10) := b(1..0);
>occurs that, for a (well-designed) generic unit, there will be certain
>(valid and meaningful) instantiations that cause such 'null assignments'.
When null arrays, then an error is raised on a mismatching lengths, by
AARM 4.6(37), which says:
| If the target subtype is a constrained array subtype, then a check is
| made that the length of each dimension of the value of the operand
| equals the length of the corresponding dimension of the target subtype.
| The bounds of the result are those of the target subtype.
There is something unsatisfactory with the handling of empty strings.
In general, the upper and lower bound of a string can be negative.
An incorrect type of coding is to use Natural for the lower bound of a
procedure A is
procedure P (Str : String) is
Low : constant Positive := Str'First; -- <- Constraint_Error here
-- High : constant Natural := Str'Last;
S : String := (4 .. 8 => ' ');
T : constant String := S (-9 .. -10); -- <- Want sliding to (1..0) ?
begin -- T'First = -9, T'Last = -10
-- P (Str => S (-9 .. -10));
P (Str => T);
Is that a significant defect?.
There could be automatic sliding for null strings.