Re: Get_Line

["Matthew Heaney" <mheaney@on2.com>]

"Justin Birtwell" <jbirtwell@yahoo.com> wrote in message
news:B7Cv9.32984$iV1.11543@nwrddc02.gnilink.net...
>
> I'm having some strange behavior with Get_Line.  In a procedure called
> GetData I call Get_Line to receive input from the command line. The first
> time this function is called it behaves fine prompting the user for input.
> The second time it runs  the execution passes through Get_Line and no
prompt
> appears on the command line.  Upon doing a little research in the Ref Man.
> I found a statement that talks about if Get_Line finds a line terminator
it
> automatically returns.  But how can this be?

You might want to read my get_line article at adapower:

http://www.adapower.com/lang/get_line.html

Get_Line indicates that the entire line has been consumed by returning fewer
characters in the read request than are available in the buffer.

For example:

declare
  Max_Length : constant := 80;
  Line : String (1 .. Max_Length + 1);
  Last : Natural;
begin
  Get_Line (Line, Last);

  if Last < Line'Last then
     --entire line was consumed
  else
     --entire line was NOT consumed
  end if;
end;

There are two approaches for handling the case that not all input was
consumed:

1) decide by fiat that the input was too long, and demand that the user
enter something shorter:

Line : String (1 .. Max_Length + 1);
Last : Natural;

Read_Response:
loop
   Put ("ready: ");

   Get_Line (...);

   exit when Last < Line'Last;

   Skip_Line;

   Put_Line ("input too long; try again");
end loop Read_Response;


2) simply copy what you read into an unbounded string, and then consume the
rest of the line as necessary:

Input : Unbounded_String;

Put ("ready: ");

Read_Response:
loop
   declare
      ...
   begin
      Get_Line (...);

      Append (Input, Line (Line'First .. Last));

      exit when Last < Line'Last;
   end;
end Read_Response;


These two techniques will satisfy the majority of most programmers' needs.