Лаба 5 вар 9 / 1 / Unit1

unit Unit1;

interface

uses
Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
Dialogs, StdCtrls;

type
TForm1 = class(TForm)
Label1: TLabel;
Edit1: TEdit;
Label2: TLabel;
Button1: TButton;
procedure Button1Click(Sender: TObject);
procedure Edit1KeyPress(Sender: TObject; var Key: Char);
procedure Edit1Change(Sender: TObject);
private
{ Private declarations }
public
{ Public declarations }
end;

var
Form1: TForm1;

implementation

{$R *.dfm}

procedure Control(var Symbol:char; Pole:string);
begin
case Symbol of
'0'..'9': ;
#8: ;
'-': if Pos('-',Pole)<>0 then Symbol:=#0;
',': if Pos(',',Pole)<>0 then Symbol:=#0;
else Symbol:=#0;
end;

end;

procedure TForm1.Button1Click(Sender: TObject);
var x, y:real;
begin
x:=StrToFloat(Edit1.Text);
if x<(-pi/2) then y:= Cos(x)
else if x<=0 then y:= 0
else y:=1;
Label2.Caption:='y='+FloatToStr(y);

end;

procedure TForm1.Edit1KeyPress(Sender: TObject; var Key: Char);
begin
Control(Key, Edit1.Text);
end;



procedure TForm1.Edit1Change(Sender: TObject);
begin
if (Edit1.Text='')
or (Edit1.Text='-')
or ((Pos('-',Edit1.Text)<>0) and (Pos('-',Edit1.Text)<>1))
then
Button1.Enabled:=False
else
Button1.Enabled:=True
end;

end.