Re: unsigned type

[anon@anon.org (anon)]

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        Wrong re-read RM 3.5 (8) An Empty string may be a "Null range" string 
but zero ( 0 ) is not within the subtype of the Positive type. The second 
sentence of RM 3.5 ( 8 ) forces the index to be valid for all references 
including a null range statement.  Also, as I pointed out to Adam, about 
"Ada.Command_line" there may be other sections that may strengthen or may 
redefine RM 3.5 ( 8 ). 

        A : String ;
        ...
        A ( 1..1 ) -- is a valid string with a null range also equal 
                   -- to character reference of A ( 1 )  

        A ( 0..0 ) -- is not valid because the index range is not within 
                   -- the valid range of the subtype Postive. 
                   -- And at least the compiler should of trap the error.
                   -- Or is this a Compiler Bug!
  
RM 3.5
8   A range is compatible with a scalar subtype if and only if it is either a
null range or each bound of the range belongs to the range of the subtype.  A
range_constraint is compatible with a scalar subtype if and only if its range
is compatible with the subtype.


        And name calling show just how childless you are.



In <t43a2h.upd.ln@hunter.axlog.fr>, Jean-Pierre Rosen <rosen@adalog.fr> writes:
>anon a �crit :
>> For Strings:
>>                           --  'A' is a zero length string, A'Last = 0, and
>>                           --  put_line  ( A ( A'First .. A'Last ) ) ;
>>                           --  does not raise an Constraint_Error even though in  
>>                           --  this case it translate to:
>>                           --  put_line  ( A ( 0 .. 0 ) ) ; 
>>   A : String := ""        ; 
>> 
>> Since you can have zero length string , the index is Natual instead of Positive, 
>> because zero is in Natural but is not define in Positive. Even though the 
>> Standard package define String index as a Positive type. (GNAT)
>> 
>I usually refrain from responding to "anon", but this is so wrong that I
>have to... (Note: in French, "anon" is a young donkey; maybe that's
>where he got his name from...)
>
>The index of String is Positive, full stop. A'Last is 0 because null
>ranges are treated specially to avoid spurious Constraint_Error. See 3.5(8)
>-- 
>---------------------------------------------------------
>           J-P. Rosen (rosen@adalog.fr)
>Visit Adalog's web site at http://www.adalog.fr