Re: wait does not perform as expected

[AdaMagica <christ-usch.grein@t-online.de>]

Dmitry A. Kazakov schrieb am Donnerstag, 23. Februar 2023 um 21:41:16 UTC+1:
> It is to expect it to work with the "standard" terminal [emulator]. 
> Anything else is a long shot.

Right, there may be weird file kinds where Get_Immediate fails.

Niklas Holsti schrieb am Donnerstag, 23. Februar 2023 um 19:29:36 UTC+1:
> On my system, if Look_Ahead uses getc and ungetc, it seems Get_Immediate 
> does not use the same buffers, and has no effect on those buffers. That 
> could be desirable behaviour in some cases, undesirable in others. 
> 
> On AdaMagica's system, it seems that Get_Immediate uses the same buffers 
> as Look_Ahead (getc/ungetc).

I further experimented.

  loop
    Get_Immediate (Char, Avl);  Put ("Get_Immediate: '" & Char & "', Available   => " & Avl'Image);  New_Line;
    delay 1.0;
  end loop;

Run in GPS, it behaves strangely (seems to be one of Dmitry's weird files)

ab c<return>
Get_Immediate: 'a', Available   => TRUE
Get_Immediate: 'b', Available   => TRUE
Get_Immediate: ' ', Available   => TRUE
Get_Immediate: 'c', Available   => TRUE
Get_Immediate: '
', Available   => TRUE                      long pause until:
<return>
Get_Immediate: '
', Available   => TRUE

It only reacts after <return> is pressed.

On a terminal window, the same executable reacts as I expect (this is why the delay statement is there).

Get_Immediate: ' ', Available   => FALSE
Get_Immediate: ' ', Available   => FALSE
Get_Immediate: ' ', Available   => FALSE       as long as no <return> is pressed
a                                                                         note: no <return>
Get_Immediate: 'a', Available   => TRUE
Get_Immediate: ' ', Available   => FALSE       and so on.

So bevore discussing how Get_Immediate is implemented on different hardware or different implementations, please read the RM paras I referenced and discuss them. Looks to me like the behaviour shown last is the correct one (let aside weird terminals).

Niklas, your GNAT is two years older than mine. I guess GNAT has been corrected (at least changed) in between.

If we all disagree how it should work, we should post this on Ada Comment.