Re: variable lenght strings

[Stephen Leake <stephen_leake@acm.org>]

fmdf@tiscali.it (fabio de francesco) writes:

> 1) Is it possible to use Get_Line with Unbounded and/or Bounded
> Strings?

If you are using GNAT, you can use Ada.Strings.Unbounded.Text_IO.

> 2) If not, how should user input be managed when lines length isn't
> known a priori?

Ada.Text_IO.Get_Line takes a String argument; if it isn't
filled, you can call Ada.Strings.Unbounded on it.

The tricky part is what to do if your initial guess at a max length is
too short. You can write a loop; keep appending chunks of input until
Get_Line returns Last < Item'last.

> <snip stuff about Find_Token>
> 
> Ok, please let me know if the following is the correct usage:

"Correct usage" is whatever works for your application!
> 
> 
> with Ada.Text_IO, Ada.Strings, Ada.Strings.Fixed, 
>     Ada.Strings.Maps, Ada.Strings.Maps.Constants;
> use Ada.Text_IO, Ada.Strings, Ada.Strings.Fixed,
>     Ada.Strings.Maps, Ada.Strings.Maps.Constants;
> 
> procedure Tokenize is
>         
>     S : constant String := ".symbol HP = High_Pressure    "; -- Line A
>     F : Positive := S'First;
>     L : Natural := S'Last;
>     W : String( 1..30 );
>         
> begin
>   loop
>     Find_Token(S(F..L), Alphanumeric_Set or To_Set("_."), Inside, F,
> L);

It would be best to declare a variable to hold Alphanumeric_Set or
To_Set("_.").

>     if L /= 0 then

This could be 'exit when L = 0', but it's really a style issue.

>        Put_Line( Positive'Image( F ) & ( L - F ) * ' ' &
> Natural'Image( L ) );
>          Move( S( F..L ), W );

Named association is better here; I always forget which is the target
and which the source.

>          Put_Line( ' ' & W );
>          F := L + 1;
>          L := S'Last;
>     else 
>        exit;
>     end if;

>   end loop;      
> end Tokenize;
> 
> 
> Is it correct to check the "L" value as a condition to exit the
> loop?

Yes.

-- 
-- Stephe