字符串转换为计算表达式

1.利用SQL的Exec()来计算

2.利用JavaScript来计算

3.利用逆波兰式来计算(比较复杂)

这里用JavaScript来实现

uses

  ComObj;

function TForm1.DoCaculate(exp: string): string;

var

  script: Variant;

begin

  script := CreateOleObject('ScriptControl');

  script.Language := 'JavaScript';

  Result := script.Eval(Exp);

end;



procedure TForm1.btn1Click(Sender: TObject);

var

  str:string;

begin

   str:=DoCaculate('((1+2)*3)/3');

   ShowMessage(str);

end;

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