[Lazarus] floating point mask

[ik]

You are over engineering this.
Here is what I did (not completed yet):

  TfrmCalculator = class (TForm)
    edtAmount : TEdit ;
    edtPerc : TEdit ;
    edtResult : TEdit ;
    procedure edtAmountKeyDown (Sender : TObject ; var Key : Word ;
      Shift : TShiftState );
    procedure edtAmountKeyPress (Sender : TObject ; var Key : char );
    procedure FormCreate (Sender : TObject );
  private
    { private declarations }
  public
    { public declarations }
    FloatingPoint : array [1..2] of Boolean;
  end;

procedure TfrmCalculator.edtAmountKeyPress (Sender : TObject ; var Key :
char);

 function CanFloatingPoint : boolean;
 begin
   Result := (not FloatingPoint[TCustomEdit(Sender).Tag]) and
             (Length(TCustomEdit(Sender).Text) > 0);
 end;

var
  OldSelStart : integer;
begin
  if (Key = '.') and (CanFloatingPoint) then
    begin
      FloatingPoint[TCustomEdit(Sender).Tag] := True;
    end
  else
  if (Key = #8) then
    begin
      OldSelStart := TCustomEdit(Sender).SelStart;
      TCustomEdit(Sender).SelStart := OldSelStart - 1;
      TCustomEdit(Sender).SelLength := 1;
      if TCustomEdit(Sender).SelText = '.' then
        begin
          FloatingPoint[TCustomEdit(Sender).Tag] := False;
        end;
      TCustomEdit(Sender).SelLength := 0;
      TCustomEdit(Sender).SelStart := OldSelStart;
    end
  else if (Key in ['0'..'9']) then
    Key := Key
  else         //Floating point not allowed
    Key := #0;


end;

procedure TfrmCalculator.edtAmountKeyDown (Sender : TObject ; var Key : Word
;
  Shift : TShiftState);
var
 Selected : Integer;
 OldStart : Integer;
begin
  Selected := TCustomEdit(Sender).SelLength;
  OldStart := TCustomEdit(Sender).OldStart;
  if Key = VK_DELETE then
    begin
      if (Selected = 0) then
        begin
          TCustomEdit(Sender).SelLength := 1;
          if (TCustomEdit(Sender).SelText = '.') then
            FloatingPoint[TCustomEdit(Sender).Tag] := False;
          TCustomEdit(Sender).SelLength := 0;
          TCustomEdit(Sender).SelLength := OldStart;
        end
      else
      if (Selected = 1) then
        begin
          if (TCustomEdit(Sender).SelText = '.') then
            FloatingPoint[TCustomEdit(Sender).Tag] := False;
        end
      else if Selected > 1 then
             begin
              if Pos('.', TCustomEdit(Sender).SelText) > 0 then
                FloatingPoint[TCustomEdit(Sender).Tag] := False;
             end;
    end;
end;

procedure TfrmCalculator.FormCreate (Sender : TObject);
begin
  FillChar(FloatingPoint, SizeOf(FloatingPoint) , 0);
end;


I'm thinking in creating such a component btw, if anyone is interested.

Ido

http://ik.homelinux.org/


On Wed, Dec 9, 2009 at 8:14 PM, David Emerson <dle3ab at angelbase.com> wrote:

> > David Emerson wrote:
> > > at first I overlooked "e+" which is valid for val (string, real)
>
> Alexander Klenin wrote:
> > No, it is not:
> >   Val('e+', x, d);
>
> What I meant is that I first overlooked 'e' and '+' as valid characters
> that can appear together within a string to be converted to a float.
> The following compiles and works as expected:
>
> var x : real;
> begin
>  val ('4.1e+5', x);  // "e+" is valid for val (within context)
>  writeln (x);
> end.
>
> The point I was making was that if someone is going to make a floating
> point mask (note the subject...) that one should be careful not to
> exclude any valid characters if restricting input by character. I'm not
> sure if the set I suggested ['-', '.', '0'..'9', 'e', 'E', '+'] is
> complete.
>
> Cheers,
> ~David.
>
>
> --
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> Lazarus at lists.lazarus.freepascal.org
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>
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