Re: Unbounded String to string

[Ludovic Brenta <ludovic@ludovic-brenta.org>]

tonyg wrote on comp.lang.ada:
> On 29 June, 15:33, Adam Beneschan <a...@irvine.com> wrote:
>> On Jun 29, 7:28 am, tonyg <tonytheg...@googlemail.com> wrote:
>
>>> Hi,
>>>    I have an unbounded string from a database I want to turn into a 16
>>> character subtype of string
>>>
>>> i.e. unbounded_string to string(1..16)
>>>
>>> I've been trying to do this most of the afternoon but keep getting
>>> errors
>>>
>>> anyone know how ?
>
>> Declare a subtype to give string(1..16) a name; then call To_String
>> (in Ada.Strings.Unbounded) and convert the function result to your
>> subtype.  E.g.:
>>
>>    subtype String_Length_16 is string(1..16);
>>    V : String_Length_16;
>>
>>    V := String_Length_16 (Ada.Strings.Unbounded.To_String (U));

That solution only works if U happens to contain exactly 16
characters, which is probably not the case if the database really
contains unbounded strings (i.e. VARCHAR or similar). So what you
probably need is something more elaborate along the lines of:

function To_String_16 (U : Ada.Strings.Unbounded.Unbounded_String)
return String_16 is
   Temp : constant String := Ada.Strings.Unbounded.To_String (U);
   Result : String_16;
begin
   Ada.Strings.Fixed.Move (Source => Temp, Target => Result, Drop =>
Ada.Strings.Right,
    Justify => Ada.Strings.Left, Pad => Ada.Characters.Space);
   return Result;
end To_String_16;

(some parameters of Ada.Strings.Fixed.Move have defaults; I spelled
all them out for clarity at the expense of conciseness).

--
Ludovic Brenta.