Re: Newbie, returning strings in Ada

[Simon Wright <simon@pushface.org>]

general@ciberpiula.net (Santiago A.) writes:

> 1) This case works fine:
>       Put_Line (Sock, get_line(Socket) );
> 
>    where put_line spec is:  
> 
>       procedure Put_Line (Socket : in Socket_FD'Class;
>                          Str : in String)
> 
> 2) This case works fine too:
> 
>         var U_Line:Unbounded_String;
>           ....
>         U_Line:=To_Unbounded_String(Get_Line(Sock));
> 
> 
> 3) This case fails 
> 
>         var F_Line:string:="1234567890";   
>          .....
>         F_Line:=Get_Line(Sock);
> 
> I type two characters in the client side and press enter. Everything
> seems to work fine, the server reads the first character, reads the
> second,reads the LF, enters in the return sentence and... never
> returns to the caller.
> 
> Is there any problem in a function that returns a string with lenght 2
> into a variable string(10)?
> 
> Must the returned string and the variable that will hold the result be
> of the same length?

I don't think you can have actually written

       var F_Line:string:="1234567890";

!!!

Anyway, you are quite right, the returned string and the variable that
will hold the result must be of the same length.

Fortunately you can write

  loop
     declare
        f_line : constant string := get_line (sock);
     begin
        -- use f_line

because each time you enter the declare block the compiler creates a
new f_line of the length required to hold the actual string returned
by this particular call to get_line.

(the "constant" is just a programming style thing, declare things
constant if you don't need them to be variables).