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From: Maciej Sobczak <no.spam@no.spam.com>
Newsgroups: comp.lang.ada
Subject: Get_Line problem (GNAT bug?)
Date: Wed, 06 Dec 2006 15:25:31 +0100
Organization: CERN News
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Xref: g2news2.google.com comp.lang.ada:7820
Date: 2006-12-06T15:25:31+01:00
List-Id: <comp.lang.ada>

Hi,

Consider:

with Ada.Text_IO;

procedure Hello is
    use Ada.Text_IO;

    Input_Line : String(1..100);
    Last_Index : Integer range 0..100;
begin
    loop
       Put("What's your name? ");
       exit when End_Of_File;
       Get_Line(Input_Line, Last_Index);
       if Last_Index >= Input_Line'First then
          Put("Hi, ");
          Put(Input_Line(1..Last_Index));
          New_Line;
       else
          Put("You have funny empty name.");
          New_Line;
       end if;
    end loop;
end Hello;

(please focus on the Get_Line problem here)

It should be obvious what the program does, except that the behaviour in 
the case of empty input line is a bit strange.
Below, in the right-hand column I describe what keys were pressed:

$ ./hello
What's your name? Maciek                -- M a c i e k ENTER
Hi, Maciek
What's your name?                       -- ENTER
                                         -- ENTER
You have funny empty name.
What's your name?                       -- ENTER
You have funny empty name.
What's your name?                       -- EOF
$

As you see, the first ENTER was somehow "swollowed", creating an empty 
line in the console (that's the echo of what user typed), but still 
blocking in Get_Line. All subsequent ENTERs seem to be handled 
correctly, which means that Get_Line returns with Last_Index < 
Input_Line'First.

I was already suggested that it might be a GNAT feature. If yes, it 
seems to be persistent, because I see it with two different versions.

Of course, I expect that empty lines are handled uniformly.

Any thoughts?

-- 
Maciej Sobczak : http://www.msobczak.com/
Programming    : http://www.msobczak.com/prog/