Linking Keypresses to Arrays?

[Isaac02444]

Hi there everyone! So, I've made an array for coins, like how you would put a coin in a slot and I was just wondering, how can I get the array to be done by a keypress function? This is what I have so far for the array:
-----------------------------------------------------------------------------------
program inputcash;

uses
crt,math,sysutils;

var
   total:integer
   input:array[1..9] of integer;

begin
input[1]:=1;
input[2]:=2;
input[3]:=5;
input[4]:=10;
input[5]:=20;
input[6]:=50;
input[7]:=100;
input[8]:=200;
input[9]:=0;
------------------------------------------------------------------------------

As you can see I've basically declared the array, now, each of the array values, like [1] is 1p, right?
How do I create it so that when I actually push the 1 button on my keyboard, that it adds the value of [1] into the total variable? Is there a specific code? Maybe something like...

Input:=keypress;
(further down the code)
total:=total+input;                 <<< May need another variable, opinions?

or something similar like that? Just so that I don't have to type '1' and hit enter for it to add one to the total?

Just to clarify if unsure, I want each button, so say for instance I pressed 5 on my keyboard.. Me physically pushing 5 on my keyboard, would then add the variable [5] into the total, if that makes sense?

I'm new to pascal coding, so please don't judge me because I have little understanding haha.

[codeman]

I just give you an example , you can modify it as you like ...

Add Windows  in uses ... on the top of your project.

Here is the main code...

Code: [Select]

procedure TForm1.FormCreate(Sender: TObject);
begin
    i:=0;
    total:=0;     // INITIALIZATION
end; 


AND

Code: [Select]


procedure TForm1.FormKeyDown(Sender: TObject; var Key: Word; Shift: TShiftState);
begin
     if (key=VK_1) then
     begin
         input[i]:=1;
         total+=input[i];
         showmessage(IntToStr(total));    // you can see the adding result each time you press a number
         i+=1;
         Exit;
     end;

     if (key=VK_2) then
     begin
         input[i]:=2;
         total+=input[i];
         showmessage(IntToStr(total));
         i+=1;
         Exit;
     end;

     if (key=VK_3) then
     begin
         input[i]:=3;
         total+=input[i];
         showmessage(IntToStr(total));
         i+=1;
         Exit;
     end;

     if (key=VK_4) then
     begin
         input[i]:=4;
         total+=input[i];
         showmessage(IntToStr(total));
         i+=1;
         Exit;
     end;
end;


[TS-MPS]

You could either do this via the 'ord' or 'val' functions to get a simple method of doing this.

Basically you read a keypress (always read as a character, not a number otherwise your code could fall over if user enters a non-numeric).

The 'ord' function returns the ASCII code of the input, and because '0' has an ASCII code of 48, 1 is 49, 2 is 50 etc. then if we subtract 48 from the result we will in effect get the real number equivalent. This method works because the numbers run in sequence from 0-9. Obviously this method if no use once we go past 9 though, but if fine your your purposes as you only worry about single key press.

The other method is to use 'val' function which converts a character/string into a number, which then scales up to using any number values you want.

Here's how I would do it using 'ord':

Code: [Select]

program Project1;

uses
    crt,sysutils;
var
  total: integer ;
  coinvalues: array [1..9] of integer ;
  coinpress: char ;
  AllDone: boolean ;

begin
  coinvalues[1]:=1;
  coinvalues[2]:=2;
  coinvalues[3]:=5;
  coinvalues[4]:=10;
  coinvalues[5]:=20;
  coinvalues[6]:=50;
  coinvalues[7]:=100;
  coinvalues[8]:=200;
  coinvalues[9]:=0; // press the 9 key to exit

  AllDone := false ;
  total := 0 ; // don't forget to set it to zero before starting !

  repeat
        clrscr;
        Writeln ( 'Your coin total is: ' + inttostr ( total ) ) ;
        coinpress := readkey ; // read a key press as a character value
        if coinpress in [ '1'..'9' ] then // is it between '1' and '9' ?
        begin
          if coinpress = '9' then AllDone := true else
             total := total + coinvalues [ ord(coinpress)-48 ] ;
        end else
        begin
             // invalid key press, could display a message or beep here
        end;
  until AllDone = true ;
end.


[wjackson153]

Also anytime you are wanting to use keypress on a form
you need to set keypreview  to true in your forms properties
otherwise even though you have working code

It will not respond.


Also I would add  LCLType  to your uses


then you can call its properties windows by:

LCLType.  that is a period at the end of e  wait for properties to load

this will give you a better idea about virtual keys  IE  VK_0 - VK_9

it has other Virtual Key Consants as well but to get you somewhat on the right track
this method has aided me well when dealing with Keypress Events

[Nebula]

I knew nothing about this so it's caught my imagination.

I've just added  VK_ definitions link ( http://lazarus-ccr.sourceforge.net/docs/lcl/lcltype/index-2.html ) to the wiki page
http://wiki.lazarus.freepascal.org/LCL_Key_Handling

VK_1 is hex 31, or 49, and so on up to VK_9 at hex 39

But I think the OP isn't using forms/LCL, just the CRT kind of ReadKey/KeyPressed functionality 
Thanks for the hints and tips

[wjackson153]

Ok

Earlier he made a post simarly to this one but i can not find it now, perhaps was deleted
im not sure. but in his post he was using command buttons for coin slots. So i assumed
this was the same poster as before, and he was using a gui enviroment .

Perhaps there are two students with the same project, how ironic.

[BigChimp]

Earlier he made a post simarly to this one but i can not find it now, perhaps was deleted
im not sure. but in his post he was using command buttons for coin slots. So i assumed
this was the same poster as before, and he was using a gui enviroment .

That's what I remember as well....

Perhaps there are two students with the same project, how ironic.