Delete a single character from the terminal in Ada

Question

I'm writing a program with Ada, and it reads inputted numerical characters one character a time. I'm trying to simulate a backspace button, but I can't figure out a way to overwrite or remove a character that's already been placed on the screen.

I am aware that put(ASCII.ESC & "[J") can clear the screen, but I'm not sure how it works or if it can be manipulated to delete a single character or line. I basically want to create something that can function as a backspace button, but I'm really not sure how to go about doing this in Ada. I cannot find much documentation online for this sort of thing.

Any advice would be appreciated. Here is a snippet of my code:

loop
    get_immediate(buffer);
    exit when buffer = LF;

    --Using dash as a backspace key
    if (buffer = '-') then
        put(ASCII.ESC & "[J");
    --Print to terminal if the character is numeric
    elsif (buffer >= '0' and buffer <= '9') then
        put(buffer);
    end if;
end loop;

The relevant documentation is probably the list of VT100 escape codes. — Jacob Sparre Andersen, Mar 06 '16 at 09:22
See for example [this table](http://ascii-table.com/ansi-escape-sequences.php). — Simon Wright, Mar 06 '16 at 09:26
Not sure I can remember the code for backspace, but control-G rings a bell... — , Mar 06 '16 at 21:43

score 2 · Accepted Answer · answered Mar 06 '16 at 09:25

2

From one of my projects:

procedure Put_Backspace is
   Move_Left : constant String := Ada.Characters.Latin_1.ESC & "[D";
begin
   Put (Move_Left & " " & Move_Left);
end Put_Backspace;

answered Mar 06 '16 at 09:25

Jacob Sparre Andersen

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Delete a single character from the terminal in Ada

1 Answers1