//要点18: 如果函数在接口区定义了, 就无需用 forward 提前声明了
unit Unit1;

interface

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

type
  TForm1 = class(TForm)
    Button1: TButton;
    procedure Button1Click(Sender: TObject);
  end;

var
  Form1: TForm1;

{现在函数定义在接口区(interface)}
function MyFunA(x: Integer): Integer;
function MyFunB(x: Integer): Integer;


implementation

{$R *.dfm}

function MyFunA(x: Integer): Integer;
begin
  Result := MyFunB(x) * 3; {因为在接口区有了声明, 前面的函数就可以调用后的函数了}
end;

function MyFunB(x: Integer): Integer;
begin
  Result := Abs(x);
end;


{调用测试}
procedure TForm1.Button1Click(Sender: TObject);
var
  i: Integer;
begin
  i := MyFunA(-3);
  ShowMessage(IntToStr(i)); {9}
end;

end.