unit4.pas

计算个人所得税与牛顿迭代法实现的作业源码。

unit Unit4;

interface

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

type
  TForm4 = class(TForm)
    Edit1: TEdit;
    Button1: TButton;
    GroupBox1: TGroupBox;
    GroupBox2: TGroupBox;
    Edit2: TEdit;
    Edit3: TEdit;
    Edit4: TEdit;
    procedure Button1Click(Sender: TObject);
    procedure Edit2KeyPress(Sender: TObject; var Key: Char);
  private
    { Private declarations }
  public
    { Public declarations }
  end;

var
  Form4: TForm4;

implementation

{$R *.dfm}

procedure TForm4.Button1Click(Sender: TObject);
var
  d,f,x,y,e:real;
  
begin
  y:=strtofloat(edit2.Text);         //输入0次近似根
  e:=strtofloat(edit3.Text);         //输入误差允许值
  if abs(y-0)<0.001 then
    y:=0.01;
  repeat
    x:=y;
    f:=x-Exp(x)+2;
    d:=1-Exp(x);
    y:=x-f/d;
  Until Abs(x-y)<e;
  Edit4.Text:=format('根的近似值为:%8.6f',[y]);


end;

procedure TForm4.Edit2KeyPress(Sender: TObject; var Key: Char);

var l:boolean;

begin
  l:=(key<#8)or(key>#8)and(key<#45)or(key>#46)and(key<#48)or(key>#57);
  if l then
  begin
    key:=#0;
    ShowMessage('不能输入非法字符，请重新输入')
  end;
end;

end.