Re: Computer Language Shootout

[Robert Spooner <rls19@psu.edu>]

Robert A Duff wrote:
> "Jean-Pierre Rosen" <rosen@adalog.fr> writes:
> 
> 
>>This one reads a line with no length limit:
>>
>>function Get_Line return String is
>>   Buffer : String (1..500); -- or whatever
>>   Last : Natural;
>>begin
>>   Get_Line (Buffer, Last);
>>   if Last < Buffer'Last then
>>      return Buffer (1..Last);
>>   else
>>      return Buffer & Get_Line;
>>   end if;
>>end Get_Line;
>>
>>In most cases, there will be only one call, while having no upper limit.
>>The size of the buffer is just a matter of optimization.
> 
> 
> This is a nice trick, but I suggest you grow the buffer exponentially,
> in case lines are very long.  Like, double it on each recursion level.
> 
> Too bad this was not included in Text_IO itself.  It would save
> beginners a lot of trouble.  Sigh.
> 
> - Bob
I tried this using the following program and gnat version 3.13p on 
windows professional 2000 with the following result:

with Ada.Text_IO;

procedure No_String_Length_Limit_Test is

    package Tio renames Ada.Text_IO;


    function Get_Line (Buffer_Size : Positive := 1) return String is
       Buffer : String (1..Buffer_Size);
       Last   : Natural;
    begin
       Tio.Get_Line (Buffer, Last);
       if Last < Buffer'Last then
          return Buffer(1..Last);
       else
          return Buffer & Get_Line (2*Buffer_Size);
       end if;
    end Get_Line;


begin -- No_String_Length_Limit_Test

    loop
       Tio.Put ("Enter a message, <Return> to exit: ");
       declare
          The_Message : String := Get_Line;
       begin
          exit when The_Message'Length = 0;
          Tio.Put_Line ("The message is " & The_Message);
       end;
    end loop;

end No_String_Length_Limit_Test;

no_string_length_limit_test.adb:16:26: ambiguous operand for concatenation
no_string_length_limit_test.adb:16:26: possible interpretation at line 8
Done--error detected.

Can someone tell me why the operand is ambiguous?

Bob
-- 
                             Robert L. Spooner
                      Registered Professional Engineer
                        Associate Research Engineer
                   Intelligent Control Systems Department

          Applied Research Laboratory        Phone: (814) 863-4120
          The Pennsylvania State University  FAX:   (814) 863-7841
          P. O. Box 30
          State College, PA 16804-0030       rls19@psu.edu