Delphi 中的 IfThen 函数 - 回复 "深挖洞、广积粮" 的问题

问题来源: http://www.cnblogs.com/del/archive/2008/11/14/1120015.html#1370413

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StrUtils 单元和 Math 单元 分别有一个 IfThen 函数, 举例:

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unit Unit1;interfaceuses  Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,  Dialogs, StdCtrls;type  TForm1 = class(TForm)    Button1: TButton;    Button2: TButton;    procedure Button1Click(Sender: TObject);    procedure Button2Click(Sender: TObject);  end;var  Form1: TForm1;implementation{$R *.dfm}uses StrUtils, Math;procedure TForm1.Button1Click(Sender: TObject);var  a: Integer;  str: string;begin  a := 1;  str := StrUtils.IfThen(a > 0, 'aaa', 'bbb');  ShowMessage(str); {aaa}  a := -1;  str := StrUtils.IfThen(a > 0, 'aaa', 'bbb');  ShowMessage(str); {bbb}  a := 1;  str := StrUtils.IfThen(a > 0, 'aaa');  ShowMessage(str); {aaa}  a := -1;  str := StrUtils.IfThen(a > 0, 'aaa');  ShowMessage(str); {}end;procedure TForm1.Button2Click(Sender: TObject);var  str: string;  num: Integer;begin  str := '万一';  num := Math.IfThen(str <> '', 99, 11);  ShowMessage(IntToStr(num)); {99}  str := '';  num := Math.IfThen(str <> '', 99, 11);  ShowMessage(IntToStr(num)); {11}  str := '万一';  num := Math.IfThen(str <> '', 99);  ShowMessage(IntToStr(num)); {99}  str := '';  num := Math.IfThen(str <> '', 99);  ShowMessage(IntToStr(num)); {0}end;end.