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.