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From: Niklas Holsti <niklas.holsti@tidorum.invalid>
Newsgroups: comp.lang.ada
Subject: Re: wait does not perform as expected
Date: Thu, 23 Feb 2023 19:35:46 +0200
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On 2023-02-23 16:26, AdaMagica wrote:
> Niklas Holsti schrieb am Mittwoch, 22. Februar 2023 um 18:36:06 UTC+1:
>> On my system, Get_Immediate does /not/ use the inputs collected (but not
>> "consumed") by Look_Ahead, but instead checks if there are _new_ input
>> keystrokes. If there are none, Get_Immediate returns "not Available"
>> (Hit is False) and so the loop continues.
> 
> Are you sure?


That is what I observe.


> With GNAT Community 2021 (20210519-103) targeting x86_64-w64-mingw32,
> 
>    loop
>      Look_Ahead    (Char, EoL);  Put ("Look_Ahead:    '" & Char & "', End_of_Line => " & EoL'Image);  New_Line;
>      Get_Immediate (Char, Avl);  Put ("Get_Immediate: '" & Char & "', Available   => " & Avl'Image);  New_Line;
>    end loop;
> 
> I get:
> 
> ab x<RETRUN>
> Look_Ahead:    'a', End_of_Line => FALSE
> Get_Immediate: 'a', Available   => TRUE
> Look_Ahead:    'b', End_of_Line => FALSE
> Get_Immediate: 'b', Available   => TRUE
> Look_Ahead:    ' ', End_of_Line => FALSE
> Get_Immediate: ' ', Available   => TRUE
> Look_Ahead:    'x', End_of_Line => FALSE
> Get_Immediate: 'x', Available   => TRUE
> Look_Ahead:    '0', End_of_Line => TRUE
> Get_Immediate: '                                          <- This is the EoL
> ', Available   => TRUE
> 


On my system:

ab x<RETURN>
Look_Ahead:    'a', End_of_Line => FALSE
Get_Immediate: '', Available   => FALSE
Look_Ahead:    'a', End_of_Line => FALSE
Get_Immediate: '', Available   => FALSE
Look_Ahead:    'a', End_of_Line => FALSE
Get_Immediate: '', Available   => FALSE

and so on for ever, with Look_Ahead never waiting for new input.

The behaviour on my system is certainly different from yours. I can see 
that both behaviours could be useful, depending on the program's needs. 
However, I was certainly surprised to see my system's behaviour, and a 
priori I expected to get the behaviour you see.

My system is oldish:

GNAT Community 2019 (20190517-83)
macOS 10.14.6 Mojave

This difference appears when mixing Look_Ahead and Get_Immediate, which 
seems to make no sense for the original question, and which I advised 
the OP not to do. Using just Get_Immediate should give the OP what they 
want.